No, voting shouldn't be mandatory in the United States, but it is important that you vote. Voting is very important even if it may seen simple and pointless. Millions of American didn't want Donald Trump to win, but he ended up winning anyway. Did you know that there were thousands of Americans that didn't vote that could've made a difference? Some people voted for people that they knew wouldn't win because they didn't like Hilary or Trump, but little do they know that they make a dumb decision.
Think about it, let's say you voted for Ted Cruz. Most people didn't even know that Mr. Cruz was running, but I bet that a few thousands would've voted for him because they didn't like the popular candidates. Everyone knew that Cruz wasn't going so win so you basically wasted your voice. The smarter thing to have done was voted for the candidate you liked best (out of Trump and Hilary). So if you didn't want Trump to win and you was one of those who did a pointless vote, you need to put the blame on yourself.
The point I'm trying to make is voting is very important. You voting could've made the difference between a candidate winning or losing a state. Like I said, voting is important but it shouldn't be mandatory because you can't make someone do something that they don't want to do. Although many people wasted their voices, where will be another chance for them during the next presidential election. In conclusion, take time out and think before you cast your next vote.