I highly suggest reconsidering this decision. You make a fatal error by embracing this nationalistic illusion of separation. You are not a citizen of America: you are a citizen of the world, the Universe. Fight for your world, not your country. Borders are purely illusions that reinforce the misconception that we are separate. We are innately one, all descendants of the singularity, all appendages of the Universe, however, we are the privileged components of this complex, capable of deciphering this beauty.
Are you sure you want to fight for oil, money, corporations, and fear and hate? You want to do this for liberty and justice? What difference does that make to the dead, the widowed, the homeless, the orphans that will come to be because of your and your allies actions?
Examine the statistics of people who engage in warfare. More Vietnam veterans have killed themselves than were killed during the Vietnam war. PTSD, depression, and constant anxiety are rampant and commonplace among those unfortunate to serve for their country. They live lives of suffering and unfulfillment. There are causes worth dying for, however, certainly none worth killing for. And don't fool yourself, killing under the instruction of government holds no difference in contrast to killing by your own desire, and people who kill are not to be praised, however, condemned.