You're assuming the US has a choice.
The question is what would they get out of no longer tolerating the devil they know and would it be worth it? I lack the imagination necessary to see how the answer is anything but nothing and no... beyond nationalistic political bullshit.
A lot of other countries don't particularly like the idea of the US being in charge of this global resources, and they are already preparing their own root DNS servers.
More the merrier.
It's not that hard, mirror the current root node and then start forking. Maybe do
a bit of censorship
They can censor whatever they want at their borders using an infinite number of methods all much more effective than operating a root server.
, maybe make sure nothing resolves to google.com without a giant cheque.
The second they do this is the second their root servers are permanently delisted from every other operators root list.
International governance doesn't make the problem go away, censorship already exists to a degree, but it makes it politically easier to keep everyone on the same network.
I despise what ICANN has become and prefer IANA free itself as quickly as possible. Personally fully on board with multi-stakeholder assuming details are sound and not likely to be captured by government and industry any worse than under ICANN's reign.
In my view what we should be afraid of is not so much censorship as it is irrational policy that leads to chaos: (Domain tasting, VeriSign wildcards, domain extortion rackets, copyright/trademark regimes) The TLDs and especially ccTLDs wield all the real power to the extent DNS conveys any at all.