I don't either of these statements are fair comment. One could equally argue that electing Congress or the President by popular vote is to treat the people of the smaller states as less important than the 15 largest states. Which would easily determine the outcomes of those elections, giving a person who moved to one of those largest 15 states far more electoral power than if they moved to one of the smaller ones.

But this whole debate misses the point. Regardless of whether the President is elected by popular vote or not, under the current system the Presidency will always be controlled by the Republicrat party, whether its centre-right neoliberal wing, or its hard-right neoconservative wing. Breaking that duopoly is where proportionality matters most in the US system.

Replacing FPP (First Past the Post) vote counting with STV is how you do that. So people can vote for a left-wing candidate without splitting the vote and handing the election to the hard right. 

 ... and I ought to add, given the inclinations of many of Nostr, that it would also allow right-leaning libertarians to vote for candidates who actually reflect their views, without handing the election to the authoritarian centre-right (Dems).

In either case, STV in local and state elections would diversify representation at those levels of government. Which would likely filter up to Congress and the Presidency, whether STV voting was used at that level or not. Making electoral reform there more likely to happen.