If they have become a citizen of PR and aren't solely there on vacation (I believe the laws that define state citizenship themselves vary state-by-state), yes, they can't vote in federal elections. There are still local and territory-wide elections they can vote in.
This is silly, yes. The answer is making PR a state, but historically they haven't wanted to be one and Washington has been hesitant to make them one. Here is a short video on the matter which coincidentally was published a few days ago: https://www.youtube.com/watch?v=Mk6JrUYLyWw
> The answer is making PR a state, but historically they haven't wanted to be one
It is worth noting that the last three referendums on the topic in PR all ended with a result indicating support for becoming a state, the final one in 2020 being unambiguously clear on the matter.
If a German citizen moves to France, they don't become a citizen of France (at least without eventually applying for it)
If a US citizen from Idaho moves to France, they likewise don't become a citizen of France
Is the problem that US citizens that move from Idaho to PR are not allowed to vote at their previous address, but US citizens who move from Idaho to France are?
A person who moves from Idaho to PR doesn't immediately become a citizen of PR, just like with France and Germany. They would still be eligible to vote absentee as a citizen of Idaho unless and until they become a citizen of PR.
Heck, I've voted absentee in my home county in California once while I was living in a different county in California.
This is silly, yes. The answer is making PR a state, but historically they haven't wanted to be one and Washington has been hesitant to make them one. Here is a short video on the matter which coincidentally was published a few days ago: https://www.youtube.com/watch?v=Mk6JrUYLyWw