I think the time is ok. If anything, it could probably be a little less, given the high average score. There are only 15 answers in the quiz, and the pool of US states is smaller than countries or capitals. Too much time and people would just have time to make lots of guesses.
No, agree with the OP. This needs more time. Yes, there are only 15 answers, but there is no ability to skip one and come back to it later. Get stuck on one of the answers early on and you'll never make the up the time.