Citizenship - I was in a squadron with a gent who had dual citizenship, US and Israeli. He was Jewish, and after college, before joining Marines, he enlisted in the Israeli army and fought on the Lebanese border with them. So AFAIK, the issue didn't rear its ugly head until he was going through the clearance process for TS. At that point he was already flying Hornets in a fleet squadron with a Secret clearance.
Drugs - I have never, ever, not once, done illegal drugs. I was surrounded by them in college, and when I would walk into a fraternity brother's room, they would tell me "hey Sam, we're about to smoke a bowl." My response was always "ok, thanks, I'll be back in 15-20 minutes." No big deal.
Drinking - I had a few drinks my freshman year, but didn't really get into it until my sophomore year. Obviously that means I drank under age. Reality here is you want agressive type A personalities doing what we do. Aggressive type A personalities tend to drink a little, maybe speed a little, etc, etc. You're not going to get kicked out because you go home and have a few beers or if you speed 10 over. What gets guys kicked out is when they get arrested for public intoxication and then resisting arrest, or for driving their sports car or crotch rocket at 100 mph+. I've known guys who have done that. Drinking is one of the few areas in society where there is a double standard on the law for college students. If you are somewhat responsible/careful, you can get away with it. If you are not in college or enlisted, you tend to get the book thrown at you.
My opinion only, and based on my experience, is that if you are careful and don't over do it, you will be ok. That said, if anybody ever asks you if you've been drinking though, and you have, you have got to fess up about it. There's room in the service for guys who do things they shouldn't be doing, but not for guys who lie about it.
My opinion only, and based on my experience, is that if you are going to do something you know you shouldn't be doing, be a man and just do it and keep your mouth shut, don't go looking for endorsements to break the rules. There's a 5 letter word that starts with p and ends with y associated with doing that.
