If Google had the guts to pull out of China, why not threaten to pull out of US?

A lot of media have compared SOPA to the Great Firewall of China. While they are quite different in my opinion (and not the point of this post), I wonder why Google doesn't threaten to pull out of US because of SOPA. Google could then ignore this non-sense and find the "Hong Kong" of United States (maybe Canada?), and recreate the free web there.

Maybe we can get enough sites behind this to send a message to Congress.