Even without a nuclear conflict, the United States would crush China in a conventional war. Several advantages would bring a US victory:
Naval power: Our navy has a full-load displacement over ten times that of China’s (cite), and we have 24 aircraft carriers to China’s zero aircraft carriers. With air power increasingly relevant, aircraft carriers are generally considered the most important tools in
conventional warfare today, and our carriers alone could probably cause significant damage to China. Some analysts argue that China lacks the ability to project power even out to Taiwan due to the lack of an offensive air force and blue-water navy (cite).
**Forward Basing: **In addition, our close ties with many nations in the region, including Japan, Thailand, India, Singapore, and Vietnam, would enable us to maintain forward basing which would put China on the defensive (cite). There is little chance of China gaining access to similarly local bases from which they might strike at the US heartland.
**The Economy: **Furthermore, the United States has a significant economic advantage so that any sustained conflict would tip in the favor of the Americans. China’s economy is based on exports to the western world, and a war would almost certainly draw embargoes from western Europe, shutting down much of China’s economic potential.
**Oil: **China doesn’t have access to domestic oil supplies either, and a Navy blockade on oil imports, which would not be terribly difficult to sustain given our enormous naval advantage, could immediately bring the Chinese economy and military to a standstill (cite). Planes, tanks and ships don’t move without oil.
**Technology: ** Chinese leaders themselves acknowledge that the United States’ significant advantage in information warfare would mitigate any advantage that China has in sheer manpower (cite). Our technology allows us to get past virtually all air defenses China currently holds, and we would be able to use satellites to identify weak spots in China’s massive coastline. China is just so damn big, it’s nearly impossible to defend all of it, and information technology increases our ability to exploit that fact. In addition, the American advantage in long-range precision weaponry means that the United States is capable of waging a war while remaining out of range of Chinese forces entirely - a huge advantage. China’s missiles, on the other hand, are virtually all ground-based, so that airstrikes could take them out, are short- and medium-range, so that they couldn’t strike the United States homeland, and lack the guidance capability to strike moving targets like American ships at sea or carriers(cite).
**Experience: **China has not fought a major war since Korea (where the US Air Force pummeled the PLA), while the United States has had plenty of conflicts to learn and grow a competent staff. Practice may not make perfect, but it’s much better than sitting on the bench doing nothing for decades (cite).
And don’t let Iraq fool you. The United States Pacific Command (PACOM) has many more warships, submarines, and troops than the US Central Command which is in charge of the Middle East (cite). In fact, CENTCOM borrows most of its troops from PACOM.
Now, let’s say the conflict went nuclear. Would they have a chance? Probably not.
China has all of 30 ICBMs which haven’t been updated for 25 years. They are unfueled and unarmed - basically, they are falling apart (cite). Also, remember from above that China lacks the technology for precision guidance systems, so these nukes, if launched, probably wouldn’t even hit their targets. These figures of only 30 ICBMs are probably quite accurate. The US intelligence community is pretty damn good at finding nukes - Iraq proved that, if anything, we overestimate our rivals’ nuclear arsenals.
In addition, China has never assigned nuclear missions to any of its planes, and its sole ballistic missile submarine, the Julang-1, hasn’t been deployed (cite). This gives the United States a huge advantage on the nuclear level. The nuclear triumvirate of subs, missiles, and bombers gives us the capability to easily beat China. Subs and bombers are capable of taking out China’s missile silos within hours, which prevents nuclear retaliation. A single Trident submarine could deter China’s entire nuclear force seven times over (cite ) An attempt by Beijing to ready its nuclear arsenal in the midst of a crisis with the United States would amount to suicide.
The answer to your question then, is that the United States would win in a landslide. Perhaps in twenty years, China might be more capable. For today, however, they aren’t close to our military power.