Yes, you've just described one method the US authorities use to block websites.

They also force ISPs to block IPs [0].

I feel trying to say that's not "blocking websites" is playing games with words, and the results are functionally the same to the "average" user.

The fact that the US effectively claim juristiction over the root DNS system is a more a geopolitical power thing rather than a legal restriction.

[0] https://torrentfreak.com/us-court-orders-every-isp-in-the-un...

The US arrested and imprisoned the bosses of multiple UK-based gambling sites that were not only legal in the UK – they were listed on the London Stock Exchange.

And you can use cctlds to bypass this too