American Citizens Abroad (https://www.americansabroad.org/) is another non-profit organization working on behalf of US persons abroad. They are doing some great (but probably ultimately quixotic) lobbying work in favor of changing to Residence Based Taxation, and they have also spearheaded a way to have a US bank account even when you aren't able to be physically present.

Their newsletters also have general good advice etc. and are generally a great resource.