People dont vote enough because they are not forced to. Obviously if you dont care you wont go, but as soon as the mayor/president/prime minister or anyother elected fellow does something wrong, everyone gets mad, even the people who dont vote! If you would of voted maybe you wouldnt have these "problems".
Voting in elections has been and always will be a completely voluntary thing. You aren't required to do it, but it's great when you do. If it were required, we would have people who do not care either way who wins, and just check a familiar name. Who needs that? If you don't know who to vote for, I say you probably shouldn't.
Forcing Americans to vote would be a bad idea. Americans who don't care or have no idea of the issues involved would most likely not spend the time needed to become acquainted with the issues. Instead, they would conduct a quick internet search, accept the suggestions of friends or family, or just randomly select names. (Plenty of voters do at least the first two anyway!)
The value of thinking Americans' votes would go down, and the probability of voting-for-hire would increase.
Bottom line: we don't want people who don't care voting.