You're grades aren't bad. They're above what the majority of people would get in the classes that you are taking. Getting into a college is not a tough task and you're grades are good enough to get you into a decent one.
First of all, I think that it's important to follow what you really want to do in life, first and foremost. I know everyone will say that you won't make money and etc. But if You feel that the best thing to do is to travel from place to place making a difference, then you SHOULD do that. It might be a tough life thinking about the culture of the USA but that shouldn't stop you if that what you want to do with your life. So forget what everyone else is telling you. You know what you want to do and nothing should stop you from trying to do that (assuming that it isn't being a serial killer or something heinous like that). So that's a decision that you have to make and make alone. If you need help deciding, talk to a counselor or somebody you trust and talk it out with them. But keep the conversation on what you want and not what they expect you to do or want you to do.
Second, if you are worried about your grades and you do decide that college is important, then there are a few things you can do. First of all, you have to decide that a degree is important to you and that you want to get one. Once you decide on that, it will be much easier to focus on what you need to do to get good grades. Second, ignore the grades for just a second and think of school as an educational process. The grades are not the main goal. The main goal is that you learn everything that you need to learn and more. If you focus on learning the material and not worry about your grades as much, you will find that you get good grades. Good understanding of the material = good grades for the most part. Not the other way around. So try to learn everything you can about the material and understand it. Then the grades will come once you do that.
And don't compare yourself to anyone else.

You are a different person with different aptitudes. And you shouldn't judge how good you are according to what other people can do. Trust me. You're smart enough and good enough. So keep your head up and stay true to yourself. Follow what you want to do (: Good luck.