The pressure to rile up voters exists either way. You saw this in the UK recently, where there are plenty of parties, and the election was incredibly awful. The winner of the election was, as usual, the one that had eliminated the second, third, and fourth parties that split the vote.

I'm not saying there aren't differences, but I think it might help Americans to think of it as if it were more similar. They cast one vote, and if their candidate lost, they get to vote for their second favorite. It's not identical to a runoff election, but there are enough similarities to make me believe that a change to true runoff elections would not alter how people perceive the result.