The gerrymanders are not even the main cause - reasonable maps in Ohio, North Carolina, Michigan, Pennsylvania, and Wisconsin would combined swing MAYBE 6-7 seats, but probably less.
Dems' problem is a simple one: their voters self-pack. The constitution places a large value on geographic diversity and winning individual states, and on both measures Dems fail miserably.
Remarkably lazy analysis by 538 honestly.
Wrong.
Non Partisan maps in those states would swing
OH: 4 districts
NC: 2 districts
MI: 3 districts
PA: 3 districts
WI: 2 districts.
That's 14. Not 6 or 7.
What's your source on this? Not doubting you, just genuinely curious.