Not all expats are created equal. For example, Mexicans living in the US tend not to do so well in education or the economy, dragging a lot of US national statistics down. This is because a lot of Mexican-Americans come from lower class backgrounds and not Mexico's educated elites.
As another discussion pointed out on HN, Mexicans and poeple of lower class backgrounds will be referred to as "immigrants", while people from richer countries will be referred to as "expats".
I have started trying to swap the two around in my own language, to avoid stereotyping people based on class.