I had written some more explaining why, but the simple fact that you'd need to convince roughly half of US states to vote to give themselves less power means this would never happen. We can't even get reforming the Electoral College through enough blue states, and the President is supposed to represent all states.
Candidate centered more proportional systems with multimember districts (e.g., STV) could be implemented without substantially changing the state based structure or apportionment of legislative power (if you go with fixed five-member districts for the House, you'd need to increase the quantum of apportionment to 5 seats, which would somewhat shift power unless you quintupled the number of seats.)
This would leave the regional distortions in place, but address the limited-time problems of duopoly.