There’s also the fact that whether or not the undocumented are illegally voting in national elections

They're not.

Also, California and New York have lost House seats in recent reapportionments despite having large undocumented populations, because people are moving out of those states. That counters your argument.

There are a ton of illegal immigrants in red states, because people hire them there. It's not some one-sided conspiracy to get more House representation.