Pretty much all Americans who live abroad full-time are wealthy, highly skilled workers employed by multinational corporations. You don't have blue-collar Americans going to do entry-level work in Europe or Asia and wiring money back home to the folks in Kentucky.
The big difference is that if you're an American and live elsewhere, you made a conscious choice to do so. You weren't emigrating to support your poor, starving family or flee political or religious persecution. Most American ex-pats are members of the "global elite" who pretty much already have likeminded elected officials in any country they go to whether they can vote or not.
None of that is necessarily true of every American abroad and it shouldn't just be assumed in conjunction with an effort to delegitimize the right of citizens to vote.
^^^
It's actually far more likely that Americans living abroad are the children of poor immigrants or are naturalized emigrants to the US than "wealthy expats". Notice the number of migrant flows to Mexico from the US; many people in this flow are Americans of Mexican descent.
For instance, most Americans who live abroad live in Mexico (~800,000; this is comparable to the number of expats in all of the EU combined!), Canada (~300,000), the Philippines (~600,000) and Israel (~185,000). None of these countries are really filled with "wealthy American expats". While there are plenty of affluent Americans in Mexico in San Miguel Allende or Mexico City, there are likely far more Mexican-Americans who are living with family members or whatever. I imagine that the same is true of the Philippines.
Basically, it's very foolish to make assumptions about any of this. Based off of taking a cursory look at statistics, it becomes clear that the number of imagined affluent expatriates is far higher than it is reality. For instance, there are nearly as many expatriates in the Dominican Republic (82,000) as there are in Australia (90,000).