I don't necessarily disagree with your second sentence, but I don't agree with your fixes.
The changes don't necessarily happen quickly, but over time they do happen. Here is a link to a map of the states that have had >20% change in party affiliation from 1992-2013. There are 22 states on here, or almost half the country, and if you include all of the swing states that keep going back and forth then it's more likely your vote can make a difference over time than you think.
Ballotpedia: The Encyclopedia of American Politics
ballotpedia.org