Excuse me if this has been discussed before but… Hypothetically speaking, say all the money in the US was divided evenly between all the people. Would we be rich? Poor? Middle-class? I guess that could settle whether communism would work. 
I thought Ronald Reagan answeres that one. Actually my wag would be that whatever it was some time later (maybe a year maybe 10) the former rich would have most of it again and the former poor will be back to poor again.
If you take your share and start a business, you may get rich.
If you buy a house, you may break even.
If you buy drugs and hookers, you might not have your money very long.
Many rich people are rich because of the work they do, many poor people are poor because of their bad choices. This aspect of human behavior won’t change.
Quite possibly the perfect explanation for why the slave reparations movement in the 'States probably wouldn’t work.
A bit more than 40 years ago Fidel castro had the same idea: All private property in Cuba was confiscated and everyone was to have equal enjoyment of the property and its product. Didn’t work too well.
Another way to think about it would be: how would you spend your share?
The answer to the OP – if we divided up all the money that there is right now, how much would each American have?-- depends on how you are defining “money.” Are we just talking about the money supply, and if so, are we using M1, M2, M3? Are we talking about GDP? You’re going to get different answers depending on what measure you use.
Going with the simplest measure, the M1 Money supply, which consists of immediately liquidible assets, the Fed’s Aug. 8 money stock release gives it as $1.189 trillion. If you divided that equally between all 265 million Americans, that’d give us about $5,000 each.
Using M2, which adds time deposits and retail money market funds, that gives us around $5.6 trillion to play with. That increases everyone’s share to around $21,000.
M3, which tosses in institutional money market funds and some other more esoteric things like Eurodollars, gives us $8.2 trillion. Now, we’ve all got around $31,000.
Of course, as everyone else has already noted, wealth isn’t static. It’s constantly growing, and constantly changing hands.
The economy would collapse over night.
Quite simply, you need a certain amount of disproportion in the income/wealth levels to stimulate investment and research.
Its a lot harder to organise big projects with 100,000 peoples wealth that with 1.
Those who produce or do things other people need or want produced or done, would wind up with the money.
pld already discussed the redistribution of the entire “money supply” of the units known as US dollars. BTW, it’s now 288 million Americans (citizens and legal residents) so it’s even less per person. If OTOH we distribute it based on the 106 million households of the 2000 census, the share becomes some $76K/household M3, a little over $11K M1.
Hardly “Party Time”.
If we base it on redistributing the wealth of the Gross Domestic Product (the value of goods and services produced within the USA in a year including consumption, investment, government spending and net exports), it’s about $36K/year/person or a little under $100K/household. And then you’d have to find a way to make sure you spend/invest/pay taxes/yourself produce just as much over the next year in order to repeat it the following year, and the next, and the next…
A piece of paper with Andrew Jackson’s picture in your pocket is meaningless except insofar as you can hand it over to someone in exchange for that someone putting a tankful of gas in your car, or getting said car washed and waxed, or giving you internet service for the next month, or givign you a a new shirt, or paying you 2% interest when he returns it to you. And then, guess what, Andy’s picture is no longer in your pocket, is it? (But, in the latter case, at the end of the year you now have $20.40 in your pocket. “Wealth”, unlike matter and energy, CAN be created or destroyed.)