It will not smash Internet
It will smash the US' connection to the Internet.
With all the high (financial) stakes the world has in the Internet, do you really think other countries will let the US dictate to them what can and cannot be on the Net? "If the US doesn't hesitate to plain out lying and deceit in order to go to war with another country - several times in their (also recent) history -, what is to stop them from doing the same in order to shut down a site which they simply don't like?".
I don't see the Internet smashed like this. Worst case scenario is that a lot will move underground, there are more ways besides public DNS servers to keep websites and such up.
What I do see happening if this gets active is other countries putting on the pressure to get a fully independent DNS registration system which cannot be influenced "just like that" by oppression or persuasion from a single country.
And then we all get what we want. Obviously a country will keep control over its own (localized) root DNS hierarchy. How ironic; the US is one of the first to start commenting, complaining and ridiculing China's "great Firewall" only to end up doing basically exactly the same thing. Of course this time its to "protect the freedom" (and the baby's, the kittens, the good, the bad and the ugly).
