Obviously a bit of a far fetched scenario, though with the friction over the Iraq situation, anything close to this is possible.
Can the United States and Britain fight the world, and still survive? What about the United States?
There’s no parameters: you can go conventional, nuclear, WOMD, or a combination of all three!
Well, things would go nuclear and Australia and South Africa become the new world powers. Maybe Brasil, too.
My moneys on US! Best delivary platforms.
Fagjunk Theology: Not just for sodomite propagandists anymore.
In all seriousness, China and Russia will probably war on each other before they war with each other.
If it did happen, though, all of these countries would probably end up sheets of green glass.
Time to stock up on canned food, water purification kits, geiger counters, and crazy Mad Max type offroad vehicles.
plus Argentina & Uruguay
The south hemisphere rises to clean up the ashes !
World maps will from then on be printed with the south ple on top!
How about the only possible answer: the whole world loses if nuclear superpowers powers go nuts.
It wouldn’t be a video game.
I already have my selection of tribal-piercings selected (though not actually in). And my post-apocalyptic name will be ‘Persnickety Bob’. I will be such a badass, come armageddon.
But to the OP…impossible question to answer authoritatively. My guess and hope, of course, is that the incredibly superior technology and systems of the US would prevail.
But if not, get ready to have your village raided by Persnickety Bob and his band of merry pillagers…
Who wins?
That should be obvious.
No one wins. Even if it doesn’t go nuclear.
Barring use of nuclear weapons, in which case neither side wins, the US and UK have a large advantage in power projection. The US and,to a lesser degree, the UK have geographic barriers prevent land invasion.(I am assuming the chunnel gets blown up early on.) In terms of naval power, the US Fleet is probably more powerful than every other navy combined, and the UK’s fleet is probably competing with the larger but lower tech and rusting Russian navy for a distant second. For example, in terms of aircraft carriers, the US has 12 full sized (~100,000 tons) carriers as well as 11 smaller amphib vessals that carry Harriers and Helicopters. The UK has 3 small carriers, roughly the size of our amphib ships that also carry Harriers and Helicopters. In comparison, the French have 1 mid-sized nuclear carrier, and IIRC the Russians have two mid-sized carriers, neither of which is in good repair.
The US fleet would be able to fend off any serious attack on the US mainland, but a few Russian bombers might get through, as well as terrorist attacks sponsered by the above countries, but the US should come though with minimal damage to its infrastructure, barring us of WMD. Things might get bad for the UK, with a second(or third if you count WWI) Battle of the Atlantic between US escorts and cargo fleets vs French, German, and Russian submarines, and the Brits would take a heavy pounding from attacks across the channel. In the Pacific, I find it difficult to imagine a scenerio where the Democratic People’s Repulic of Korea gets into a war with the US without South Korea being involved. Again, barring nukes, North Korea can’t hurt the US directly; they could hurt us economically by striking South Korea or Japan. Now, North Korea has a larger military than the South, but South Korea’s forces are much better trained and equiped. Seoul would be pounded by artillery though. It would be even worse if both China and Russia sent ground forces in to back up the North Koreans, and the Korean pennisula would be massively wrecked.
Assuming the UK holds against invasion, the US’s high level of power projection could probably destroy most of the countries mentioned air and sea power given enough time, and most of the heavier ground equipment. But as to actual occuption, the US and UK just don’t have the manpower neccessary to occupy China or Russia, much less both at the same time. We might be able to occupy the smaller countries - Iraq, North Korea, France, or Germany, but all four of them at the same time would be severly pushing it, not to mention having to deal with ground attacks from the Russians and Chinese, where they are closer to parity with the US, compared to Sea or Air fights. Overall, I think you would see some sort of negioted peace after several years of fighting.
Thank you for attempting a STRAIGHT answer, not commentary! 
The U.S. and the U.K. would lose, big time.
Let’s assume Canada sticks with the U.S. (not implausible, I think), just to retain the geographic security of the U.S. Much like WWI, say, there’s a flurry of war declarations. Suddenly it’s the anglo-american axis versus the First and Second Worlds, with Central and South America and Africa declaring neutrality. Also, for simplicity’s sake, assume no nukes.
The U.K. gets the living shit pounded out of it by the combine air forces of Russia, France, and Germany, before the U.S. has a chance to reinforce. U.S. forces in Europe are wiped out fairly quickly (though after a valiant, if doomed, struggle). Numerical superiority simply wins the day here in the early stages, while the U.S. is unable to quickly resupply Britain. The U.K. isn’t occupied, which is difficult to do, but basically unimportant once it’s wiped out militarily; what survives of the British Navy sails for the east coast of the U.S.
Then you get stalemate. The U.S. has to seriously consider continental defence, so its power projection is severely hampered by the need to heavily patrol the Atlantic and Pacific coasts of the U.S. Effectively, this means the U.S. is unable to take the war to Europe, since what’s left over isn’t enough to conquer any but one or two countries, which is immaterial since Russia and China are the economic drivers of the war against the English speaking countries (France, Germany and the others can make significant contributions, but without knocking out Russia or China, the enemy is still fundamentally intact and strong, if only in manpower and bullets terms).
The rest of the world could cobble together an invasion fleet, but it would be risky in the extreme given American naval superiority over its coasts, along with its submarines roaming widely.
With stalemate comes the slow strangulation of the U.S. Trade basically dries up, the U.S. economy goes into the shitter, and unless peace is made quickly, America becomes a hollow shell of herself in a few years and starts suing for peace.
The key point to all this is that, if the rest of the world turned against the U.S., the U.S. would keel over fairly quickly for economic, not military, reasons. The strength of the U.S. is built on trade, and while the U.S. can withstand some instability in the world, it fundamentally requires a large number of trading partners to keep going. Look at how talk of a very limited war gives the economy jitters.
Arms and liquor merchants win. And I intend to be in on that action, baby!
A bit of justification for my claim that the U.S. loses its force projection capabilities in such a war.
The U.S. has never, to my knowledge, faced the threat of a serious invasion of North America. Against Russia, China, and most of Europe, that becomes a real possibility, given the combined manpower and naval assets of those countries–none have serious landing capabilities individually, but all together could put together a threat. Rather than make a D-Day landing in Georgia, they could invade Mexico or Canada (on the east coast) more easily, and launch a land invasion. The U.S. can’t reinforce the entire coastline of North and Central America, so it has to rely on its navy to stop an invasion fleet from getting there. With the navy tied up patrolling from Greenland/Alaska to Brazil, there aren’t enough naval assets left for force projection.
The combined amphibious landing capabilities of the rest of the world combined might give you a solid division or two. Maybe. Hardly a proper invasion force. All they would accomplish is the loss of that division or two, plus any ship that tried to bring them here.
American and British subs are the absolute finest in the world. They are also the most numerous, in a practical sense. While Russia or China may technically have hundreds of rusting 70’s vintage subs sitting at pier, the US and UK regularly deploy a larger part of their fleet then any other in the world. Those subs alone would handily defeat any attempted invasion fleet. Hell, those subs would probably be able to take out the enemy navy before it was able to deploy.
B-52’s carrying up to 32 Harpoons a piece, P-3’s, and countless other assets would be more then plenty to free up our carrier battle groups, so they can go raise a little hell.
And don’t forget, it is not the quality of our equipment that makes our armed forces great (though that quality is the absolute finest in the world), it is the quality of our training. Our forces train hard, realistically, and often.
You mention the “combined air forces of Russia, France, and Germany”. Which are outdated, not properly maintainted, and use inferior weapons on those aircraft that do manage to sortie. The RAF’s Tornados, Harriers, and Hawks, along with the USAF components already in the UK, would be more then enough to ward off some tired and ill-trained Mirage-2000N’s or Tu-22M’s.
I don’t doubt that, man for man, U.S. and U.K. troops are far better than their counterparts in this fictional war, given their training and equipment. But numbers have a quality all their own, and what’s been proposed is a huge numerical advantage for the enemy.
I don’t think a seaborne invasion could be successful. But I think that what the U.S. would have to do to ensure that it would fail would also remove the bulk of its power projection assets. And in a world war of this scale, home defense takes on a much higher priority.
Remember, there’s an economic benefit for the enemy: with the U.S. not trading with the world anymore, Russia, China and Europe suddenly have a lot of open markets to fill, which would stimulate their economies–and their war machines.
I will say that, if any one of those three–Russia, China, or Europe–isn’t in the enemy camp, then the U.S. wins. It’s the unified front that makes life hard.
You all seem to forget the cockroaches would come out on top …
Al Qaeda wins. They are akin to cockroaches.
There was a discussion about US vs the World scenario somewhere else. The conclusion is the US will lose as long as no nuclear weapons are used. Otherwise, the cockroaches win, big time.