Funny thing about the drinking. Our legal age is 16. My friend and I went to America for a semester abroad when we were 21/22. Wanna know what we experienced there? Nobody could drink responsibly! Why? Because in America you don't drink until you're in college, a time when you're on your own for the first time, in most cases, and nobody monitors you anymore. The things we saw there in college drinking were not only shocking but also dangerous a lot of times. People clearly didn't know their limits. On the contrast, here in European universities (well at least the Germany/Netherlands area), people also drink - but with great differences. For starters, I'd say the incidence of drunk driving I've experienced is a lot, A LOT lower. Then, we don't keep drinking past the point where we're puking it all back up again. We can enjoy a couple of beers or a glass of wine without getting trashed, and so far, I haven't seen people at my university end up in ERs, unconsious on the floor or whatnot either. Wanna know why? We are already allowed to drink at an age where we're a) not allowed to drive yet, b) still have parental supervision and c) don't live in an environment that allows us to get wasted every single night, without any serious repercussion.
Not really point of this, but also...you're allowed to have a gun at 18, but you're not responsible yet to drink? Sure, that makes sense.
This kinda works for sex too. First of all, this whole age of consent doesn't actually stop people from having sex. It just makes it a crime for somebody over the age of 18 to sleep with minors, but notice your point ("There is a lot of responsibility that comes with sex, and in my opinion, a 16-year-old should be thinking about school and hanging out with their friends, not about sex and the dangers that go along with it (STDs, pregnancy, etc.)." ) is in no way addresses by this, as high school kids are having sex if they want to one way or another, be it with their legal peer, or the oh so evil 22 year old. Why not let them make the choice? I'm not saying there shouldn't be any age of consent, but that's why I back up Germany's choice of 14.
Interestingly enough, the age at which you are liable for any of your criminal actions and can be sued is also 14 in Germany. This makes a lot of sense in my opinion. It levels responsibilities to one age. At 14 you're deemed responsible enough to decide yourself about sex, but at the same time you're also deemed responsible enough to stand up for any of your other actions. American laws are just arbitrary, in a lot of cases.