If they can't undo the site at the tld level, the US can still compel the DNS servers nearby to erase their record, or redirect it to a "this domain is seized" page. In extremis. they could just poison the DNS addresses of blocked websites although they dot need to.
If the DNS is located in the US then they have to comply with US law.
My point was just "the US seizing websites hosted outside of the US without that country's cooperation" simply doesn't happen because there's no way for it to happen.
