I am presuming that some of the Americans dead, abused, and hostage are not dual American by convenience citizens.
As there is war, all Americans should be told to leave or turn in their US passports and stay as citizens of the countries they choose over the US.
Well, it’d be very, very impractical if not impossible to ban dual citizenship. Sure, if you want to hold certain U.S. government jobs, they make you swear under penalty of perjury that you’re not a dual citizen, and I supposed you’d be in trouble if you were caught lying. But how ‘bout ordinary Joe Citizen? How are you going to make him ditch his Norwegian passport? How are you even going to find out he has one? I suppose that some type of international database could be done whereby all countries identify their own citizens and provide a comprehensive list to other countries for purposes cross-matching, but that’s a road that I’m not sure that we or even other countries would want to go down.