Josh,
Not that I am aware of. But, you are 18, which means that you can vote, and enlist. All you need is documentation showing birth as an US citizen, social security number, and high school grad. My biggest worry for you would be if you are classified as a "home schooled" student. If this is your dream, then do it. If your parents support you, then they will support you. If they won't, then they won't straight across the board. Your life. Live it. If this is your dream, get back to the states and enlist.
SSgt K