There are money which fly into U.S. away from political instability or economic troubles in other countries.
They usually get parked at big name cities like LA or NYC. If Chinese economy goes down, a few hundred billions of dollars could pour into U.S.. When Soviet Union collapsed, KGB funneled out $400 billion according to some reports. The same thing could happen to China on its way down. Overseas economic crises spread out over time could provide periodic injection of foreign cash into U.S. markets, especially real estate markets. They could work as a cushion which can buy time for U.S. economy.
This seems to be what is happening to U.S. Other economies fall down before U.S. does, helping U.S. economy with escaped money.
You make an excellent point.
Is there a bubble in either residential or commercial RE markets?
Think of a "flow of funds" model. Stock returns in the US have been hovering in the 10,000 - 10,750 range. Returns overseas are flat. Bond markets offer low rates. Where do Americans and overseas investors put their money? The US real estate market.
The problem will real estate price deflation will come when 1) US equity markets rebound, 2) US long-term interest rates start rising, and 3) foreign equity markets improve. Any of these outcomes will cause a flow of funds AWAY from real estate and into other capital markets.
But until then, I can't envision a "crash."
I testified to the US Senate on the real estate market. Of course, no one listened (each Senator had their mind made up before the testimony).