The Economist has a chart showing the trend of US house prices from 1920 to 2008. It shows that house prices have fallen by 18% in real terms since 2007. This means house prices have fallen faster than during the Depression in the 1930s.
European buyers are already entering the US real estate market, because they can now buy houses at very low prices. Many houses are being sold in foreclosure sales and on top of that the US Dollar is weak compared to the Euro, so Europeans pay even less than American buyers currently looking to purchase a home.
The same applies for domain names too, by the way. I've said it before: If you're based in Europe you can save a lot of money when buying domains from US sellers now!