One perspective overlooked here is the purchasing power of non-Americans (i.e., not U.S. citizens). Dollars in developing countries can be worth multiple times what they are in the United States. For example, you could help 5000 rural Vietnamese for every 1000 rural Americans. There is also a higher potential for rural Americans to obtain dollars vs. non-Americans. In utilitarian terms you have the potential to do more good by sending money to rural communities overseas.
I'm saying this as someone who loves Appalachia.
I don't have as much lived experience of someone in Vietnam as I do someone in my community. Nor do I understand the language or the culture. There's more overhead in making it happen and there will likely be a lot of things I'll never take into account or understand. On the other hand, I know what it's like living in a HCOL state where many jobs don't pay enough for a family to survive and have struggled in my own past. Could my money have more purchasing power elsewhere? Sure. And they're still people in my community struggling and I have the power to help them and a greater understanding of what they're facing. Community seems to get discounted a lot in the discussion around effective altruism and I think that's unfortunate.
The further away you are from the recipient the harder it is to see the second and third order effects. Local and small means they can be noticed, and things modified to change the outcomes.
Rural America also has a government that is fully capable of taking proper care of it's underprivileged; most governments across the world are not.
They also ignore that even if other rural areas are technically speaking more rich than the rest of the world, still struggle with an extreme shortage of opportunity, upward mobility, and sense of purpose.
I speak from experience, having been raised in one such area. Had I not moved to a tech hub in search of greener pastures (which is not something everybody is capable of), my life would look so different now as to be unrecognizable. Instead of earning the upper end of the salary band for my line of work with numerous upward trajectories to pursue and a solid bit of retirement stuck away, I'd be working a job earning maybe ~20% as much that doesn't keep track with inflation with zero mobility and an even smaller fraction of retirement funds, and that's one of the best possible outcomes in that region and inaccessible to most.
I've not aligned with the area I hail from politically for a long time now, but clearly it needs help.
positive change is slow and revenge politics makes it slower.
What difference does it make if the government is "capable" when it's not happening in practice?
A lot of areas in this country resemble the third world more than the rest of America. Don't take it from me. Try the book reference I provided and its citations.