Proportional Representation doesn't work for a single office election
11K is perhaps far too many to be manageable, but 435 is clearly far too few.
Edit: the 14th amendment may have changed this math before the 1911 Apportionment bill fixed it at 435, but 1:700K is still far too high.
If each state sends representatives according to proportional voting, we would quickly see other parties gaining some seats.
Those other parties will probably grow and even gain seats in the senate. At some point you won't need the support of all parties to break a fillibuster.
Maybe you could do PR for City Council, but the other positions are single person positions. I thought your comment was related to the article, which is why I replied like I did.
Also, however... PR has its flaws... it makes the party the unit you are voting for, not the person. Maybe you like one party member but not another; with PR, you can't make that choice, the party does.