They're not trying to. Each side's politicians are very much trying to get a supermajority voting for them. And in local areas, the skew this produces toward one side or the other is quite clear.
It's only on a national level that the parity becomes visible.
I've never seen numbers for 2024, but I have for previous recent national elections, and the most either party has in any state is roughly 70%. So at the statewide level, that's the total skew you're looking at.
In local elections, things can be more one-sided; I imagine there are a fair number of rural counties that would have only a handful of blue voters (but out of a total of, y'know, a few thousand voters in the whole county).
It's only on a national level that the parity becomes visible.