There's an interesting problem here, though, which is why the US federal government is structured as it is: there are fewer people in, say, Utah than in California. And generally people in California may have different interests than those in Utah. But as citizens of the US, Utah(ians?) deserve representation at the national level, which they just wouldn't have in a first-past-the-post popular vote. A direct popular vote would always give the advantage to candidates who represent coastal and urban interests because that's where people are overwhelmingly concentrated, and this would leave rural voters disenfranchised.

It might be interesting to re-evaluate whether representation by geography still makes sense. I'm more partial to the parliamentary approach, where parties get representation proportional to votes cast for them, so this way there could be a "rural interests party" which rural voters could vote for and receive representation proportional to their population. This might also do an end-run around the mind-bogglingly corrupt practice of gerrymandering?