Packing the Supreme Court and trying to change the Senate allocation is the point where you call it quits. The Supreme Court has been at 9 justices since basically the Jackson Era and the only person who tried to pack the Court was FDR (who was soundly drubbed for it). The Senate allocation cannot be changed, not even by amendment. Smaller states cannot be deprived of their representation without their permission.

Both would be solid signals that the US is not workable and should be dissolved.
right now the SC selection has already been completely politicized-- McConnell's actions re: Garland and today with Kavanaugh is the soft-serve version of packing the court. i have absolutely no doubt that if the GOP were to have a supermajority in the Senate, they would be considering this step now.

a softer version of all of this would be to change lifetime SC appointments to 18 year appointments, but THAT would mean a constitutional amendment. so ironically packing the court would be easier.

re: Senate allocation, no, you wouldn't need to undo it altogether-- and i agree if that were to happen, you'd be talking a new Constitutional convention or a new civil war. simply admit PR and Guam and DC as states (you don't even need to split CA into three, as some of the more wild-eyed types suggest).