In my mind, it's the word Americans use for Americans living in other countries. I doubt the locals in whatever country they're in consider them "expats." Just Americans.
The locals definitely refer to them as 'expat' or something along those lines in local vernacular.
And it's generally a Western thing, not just American or Anglosphere.
These people are completely unlike immigrants, there's almost no comparison.
If someone married a woman from Bali, moved in, was working as a manager in her Father's factory ... the term 'immigrant' might apply.
Most ex-pats are temporarily stationed, they are not there permanently, they work for international conglomerates, governments, news agencies, universities. The 'drop shipper' thing is a little specious but roughly in that category.
Me? I moved from the UK to Finland, and I'm definitely an immigrant. (As are most of the people living in the part of the city I'm in. Weird.)