It does make for an interesting thought experiment: let's say all 350 million people moved to California and Ney York, except for ~550 people. Those 550 people split into groups, and went to live in the remaining 48 states, and were either senators or representatives in the House, or Supreme Court Justices.
Those ~500 people would decide every presidency, make whatever laws they wanted to, would decide every court case, and could amend the constitution however they wanted. The rest of the people could only play within the 55 representatives of California and 27 of NY, and would never have any power to effect any national or state outcome (except those two), which the other 48 could override. This is the textbook definition of an oligarchy.
Now flip the other way: The 350 million split equally between party lines, and each states population was exactly the same. Every presidency and Senate seat would essentially be picked by popular vote, as the number of representatives in each state would be the same hence the electoral college could be a wash. Having no clear majority in any state or in any federal branch means nothing could every be passed other than legislation that a plurality agreed upon. This would be the textbook definition of a direct democracy.
So we are sliding along this scale, starting more towards the second case, but have been steadily sliding along this scale towards the first. And it's becoming more and more pronounced.