JY, first off, *do not trust anything one party says about the other.*
Silicon Valley GOP isn't going to say anything nice about the Democrats, and vice versa. That PDF does a horrible job illustrating the differences between the parties. Keep looking.
Voting *is* always important, at least in the United States. I can see the case for protest votes in emerging democracies. But by and large, our elections are free and fair so just do it.
Cynical politicians, usually those much older than our youth, *know* that the young folks will tend to vote for candidates or propositions that shake up the established order. That's why there is always a subtle undercurrent of negativity in campaigns which will turn off those with novel approaches and perspectives. Conservatives, by their nature, especially fear charting a course into unknown territory.
Our government is pretty good at representing people, but it could always be better. You've come of political age during of the greatest gridlock we've seen in recent memory, so it *seems* that government isn't doing anything.
The biggest legislative achievement of the Obama administration is the Affordable Care Act. After that was signed into law in March 2010, there has been virtually nothing due to gridlock. Normally this is not the case, but it is the norm you have experienced, so keep that in perspective.
I'll end by reiterating my first point: "Do not trust anything one party says about the other." I more frequently hear Republicans say, "Democrats want to...[destroy society / make us socialists / steal from you / etc] and it's all political posturing. If someone is selling you on how bad the other guy is, that doesn't mean he's got any better ideas, if any at all.