I'm going to be honest, I haven't read most of the thread at all. But I have some advice for you since I am an American who is <18.
Firstly, I just want you to take everything that you've been told about the USA in your homeland and flush it. From my experience with meeting those who only 'hear' about what happens here, they have it mixed up worse than my cable management. It's not THAT bad here.
To go along with that part about it not being bad here: Your local news station is going to have something I call "the fifteen minutes of unwanted fame." Basically it's all the crimes and deaths that happened overnight. Don't worry about any of that. Unless you are a gang member or drug dealer you won't get killed. Oh, that sandy hook stuff that happened, yeah that doesn't happen very much here. Even if it did, after something happens here they make sure it isn't nearly as bad.
You also are worried about bullies, for some reason. I have no idea what goes on in your homeland, but you shouldn't have an issue at all. Even if you speak in broken-English you won't have much of a problem. This is because you're not from the USA, people respect you a lot more.
You should also familiarize yourself with thinking before you speak. It's very easy to get in a ****pickle when your words don't come out right. Everyone has their opinion and can speak freely. Often times I feel getting involved in topics of politics and race is not worth my time.
Most importantly, don't be scared. You're going to start to realize everything you were worried about is completely bull****. That "fifteen minutes of unwanted fame" starts to become funny and boring after a while.
I don't live in Tennessee but I've known a few who do. They aren't to the level of Alabama, so you don't have to deal with any racist folk.
I wish you luck and I hope you will use it to your advantage. It's very hard to actually become a citizen here due to the massive waiting list. Just wait for the Trumpet to sound and then we might get in you in faster.