They take these sites down by changing the DNS entry for that site. The DNS servers they can control have to reside in the United States.
While the root DNS servers are in the US, setting up a DNS server that isn't controlled by ICANN and is outside of the US would be trivial - and I believe has already happened.
Yes but do you really believe if these laws pass they stay isolated to the United States? I believe there are already a few European countries with similar laws already passed, such as Spain (I'm a bit fuzzy on the details but I could look it up if pressed). So far they haven't really done much with those laws yet, but it's still scary the power those laws give them.
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