I must be missing something. I don't understand why not having nation wide election prevent the U.S. from having congressmen to represent those living abroad.
seats in congress are apportioned to states who then figure out how to divide them up, so while in theory a state could make an overseas district it's not something that could be done on a national level without some heavy modification to the constitution.
Since we only have two parties, each one doesn't want to do anything in the odd case it would give the other one an edge they don't know about. So things stay shitty.