I've heard that the reason Puerto Ricans can't vote is because Puerto Rico isn't a state and it is states that choose the president, not voters. But what about expats living abroad? Do they just get to pick which state gets their vote? If so, couldn't Puerto Ricans do that too?And what about people in DC? Where do their electoral college votes come from?

I'm sure I'm missing something here, I'm just not sure what.