If you are an individual investor, now is the worst possible time to leave the table.
End of capitalism? Probably not. Being one of those insane souls who enjoys personal investing, and has had decent luck, it pains me to say this: This has to happen. It's capitalism at its finest.
The financial system, apart from commercial banks started to make some really risky bets a few years ago, leveraging a lot of cash against nearly nothing. Suddenly, one of their biggest pieces of assets (the housing market) starts to implode and they're left holding their hats, which really should have come as no surprise given the number of high rated bonds to the amount of subprime mortgage companies that were out there. Something was very rotten.
Did I once consider investing in these guys? Oh, yes. Did I? Hell, no, not after I thought about it a few days.
I really do not think that the Fed or the Treasury will bail out AIG. It would set precedent about bailing out a lot of other institutions: hedge funds, venture capital firms, etc. That would not be good, and I think that there would be a lot of blowback because Joe Taxpayer is already a little perturbed by the housing crisis, energy prices, and the weak dollar. Spending more on bailing out the well-heeled would be bad press.
Fannie and Freddie were oddballs in this whole mess. They were not private sector and they were not public sector. There was a lot of blurry lines regarding what they could or could not do as a result. I think that by making them completely one or the other, things will get better. Honestly, even as a pretty staunch capitalist, it might be better in the long run if those firms are ran by the government. We might even see the emergence of similar, private firms to compete under the private sector rule-set.
Bottom line: These companies deserve to be bitch slapped by the market for their excesses, and yes, it will be painful for the rest of us. This is always the result of self-feeding in the market; I'm dating myself, but does anyone remember the fallout in the early 90s, the early 00s when the same sort of shit storm happened?
If you're wise about it, you'll just keep putting your, slow, regular amounts in, looking for good deals, and most of all, DON'T PANIC. Good deals might be difficult to tease out of the mess, but they are there, and now seems to be the beginnings of a prime buying opportunity. Remember, if you're not a floor trader, you ought not be worried about the changes over a minute, hour, or even a quarter. You're horizon is five or ten years away.
As for foreign nations holding US debt, that's tossed around a lot. It's usually not a big deal, but then again, no one thought it was before WW1 either (I highly recommend Niall Ferguson's The War Of The World for those interested in the financial and social links during the Great War (WWs 1 & 2)). On the other hand, everyone said that the Japanese would own the US by the end of the 1980s. They didn't. This time is a little wonky because Congress has raised the debt limit for the US Government several times in the past 8 years to fund some very expensive adventures, so we will probably see some serious payback in some form in the next two decades. We'll see.