I'm sure the lawmakers will love this. How soon will we see bills introduced to make it illegal to host adult sites outside of the .xxx tld?
And even if in the US porn isn't forced into the .xxx tld by law, for other countries they may jump on it much faster.
Then of course there is the issue of a slippery slope. What other content could be forced onto certain tlds by law?
Do you realize there is no actual such law? And you are already calling "them" names for something that doesn't exist?
Sure US legislators can make it mandatory for porn sites to have .xxx, however there are roughly 265 countries in the world. You'll never get every one of them to agree on regulations.
What about parents?
This is not the same as general purpose censorship, which I do not think should be made easier to censor.
Do remember that someone in a different (more permissive) country voluntarily described his stuff as porn. So you don't really have an issue of it being applied incorrectly.
Wouldn't make a difference in some places, but I bet that in some borderline cases, it could push them over.
1) Lists of blocked sites are harder to implement and make people swallow.
but
2) they aren't mutually exclusive with blocking whole domains.
Those add up to it being stupid idea.