The courts must be lenient in America. If you did that here in a bar braw for example you could be up in court for grievous bodily harm. As for martial arts it wouldent do any harm to learn some but I am sure that its not for everyone.
If you did that sort of thing in the US in just a standard "bar brawl", you'd likely be brought up on charges as well. However, if you're in grave personal danger, you have the right to protect yourself by most means necessary. There's several variables involved in every situation, but basically, if you are the one attacked, you do what you need to do to save yourself and get away.