Bitcoin never depends on the domain name, so the fundamental structure will not go down. It is the marketplace/community that may be seize. But if the community ie bitcointalk is doing nothing illegal, government cannot simply take down the site.
Aren't the Seed DNS nodes important?
Fortunately, some IP addresses are hardcoded in. Not to mention, if your client has ever connected to the network, it will first/also try IP addresses that were last seen by your node.