Answer:
Younger people have always been more apathetic about voting except in the last Presidential election. There has been a strong belief among most Americans, that the politicians don't really ever listen to their constituents and that business goes on as normal. People get fed up with the constant bickering between both political parties which leads to voter apathy.
I think the biggest problem is the unbelievable amount of corporate money that pours in to the political parties especially the GOP! It has really corrupted politics and has now made it almost impossible for Democrats to compete fairly with Republicans (some Democrats also receive large corporate donations). As a result, people are turned off by politicians getting bought off through lobbyists. This problem has the potential to undermine both parties' willingness to operate in the best interest of the electorate.
Generally speaking, people in Canada and Europe as well as Japan and Australia, are more politically astute and take the time to vote in much greater numbers than in the United States! Voting is mandatory in Australia.
A lot of people believe Congressmen are out of touch and are only concerned about lining their own pockets! People see all the great perks congressmen and women enjoy like free excellent healthcare and 8 weeks or so vacation with pay every year. This has led to much resentment and is one of the reasons why only 16% approve of Congress!