I think it's one of those "technically" things, that isn't useful.
Someone from The Americas is American, technically. That's how language works.
But I'd venture* that 97.3% of people mean United States when they say "Americans", or better, it's what people mean 97.3% of the time. The only time I've seen people bring it up is when they're from a South American country.
So I'd say context and scale of detail/granularity influence the meaning in the moment.
*Totally Made Up Stats
Yep.
But I admit I'm one of them, though I also recognize it's not an easy thing to do well. Whenever something like this comes up for a vote in my area, it really takes me a while to figure out the pros/cons, long-term implications, who benefits, etc.