But he didn't repeal a term limit. There was a two-term limit in precedent, but not in law, so FDR didn't have to repeal anything. But people saw that, and put a two-term limit in law. Any future FDR or Xi in the US will have to change the law. And yes, that will set off warning alarms in the US, if it ever happens.

Agreed.

> ... warnings won't be enough to stop it from happening.

Here I disagree. For it to happen in the US now would require a constitutional amendment. I don't see any way that would happen now. Especially since seeking one would make the alarm bells ring much louder.

Or, for it to happen now would take ignoring the constitution. I'm pretty sure that would trigger a civil war.

Either way, in the US it's much harder than just having a party congress decide that it will be so.