First off, stating your opinion does not make you a douche. If anything, the others who attacked you for your opinion are.
That being said, I do at least partially agree with you. America has gotten herself into many a thing she had no business in, but what's past is past. Like what you said about the killing of Native Americans. That's just wrong. A military should be used for defense and retaliation for acts of war brought upon by foreign nations.
Though I disagree with you about soldiers not protecting our rights. They do. We need a military to protect our country, and by extension, the rights that come with that country.
Now, I probably have a biased opinion, as I am going to join the Marines, but I join not for love of war, but instead for the ideals that America says she stands for. The protection people, not the mindless killing of them. The equality of all people.
Besides, article 92 of the Uniform Code of Military Justice states that you have to obey any lawful order, emphasis on lawful. I think ethical should be added to that. I know at least one country has that, but I can't remember which one right off of the top of my head. Russia, maybe. I plan on using this to its fullest extent.
God and country, that is who I choose to fight for.