More people voting in the US → The political conversation shifts left as more progressive/leftists candidates are viable. A lot of elections in the US happen in small amount of votes, also known as narrow margins.
People not voting because not voting for the perfect candidate feels icky → As the conservative candidates are more favoured by people voting less, this shifts electoral politics right.
I would prefer to live in a world where Americans would vote between centre and left candidates, for instance, than centre and right (relatively speaking, of course) as they do today.