I don't disagree with the premise. Not at all. I've long considered the US political system to be generally broken, but has the majority of the population just comfortable enough to not stir the pot. Election preferences notwithstanding, the current situation is about as "stirred" as it's been in many decades.
If there is a common theme in the posts in this thread, it's the inconsistency between the states. There's a reason for this. The US Constitution puts all electoral power in each individual state to decide for themselves.
Whether intentional or not, the Constitution can be somewhat vague when it comes to elections and how the Congressional members and the President are chosen, beyond some interesting verbiage about Congress choosing the President.
Anyway:
The Constitution of the United States: A Transcription | National Archives
It may be worth remembering - the Constitution was written when not everyone was convinced the idea of a central Govt was a good idea (not much changed here) and maybe each state would be better off on its own. So a lot of the text tries to create a delicate balance of States doing their own thing within an agreement between them. Defense-wise, they knew they were better off together than on their own.
I generally agree with the idea of attempting to make changes locally first. When successful, push towards the State level. It gets difficult at the state level simply due to how Senators and Representatives work.
It's hard to have proportional representation in the Senate when each State only gets two senators. In most cases, proportional representation would mean one from each party. Any 3rd party is SOL.
The House is different since each state is split into Congressional Districts, although these districts are not defined in the Constitution and may be open to change. I don't see anything in the Constitution or the Amendments prohibiting a State from instituting a proportional method of choosing Representatives different from the current Congressional District method. It would be a change to voting more for political parties than individuals although I'm sure in each race there would be a group of leaders within each party who would generally be known persons. As such, when voting for a party, one can be fairly confident in who would be the #1, #2, #3, and so on for the proportion of the vote received.
An argument against the above would be in the cases of states with a strong split between rural and city voters. It could be argued a proportional voting system would heavily favor more populated areas, but I'm not sure it would be all that different from the existing system. More analysis required.
I originally thought this discussion got deleted. Glad to see it's still here and is remaining civil.