You seem to think that by pointing out the flaws of the US military you can then draw a direct comparison with Caesar's army. For all its imperfections, you can't let a few bad apples from the former justify a brutal ideology practiced by the latter. As far as this issue of corruption, collateral damage, and a shaky justice sysyem; sure, the US military has a lot to improve on but I feel that this is a different argument. It's also dishonest to claim that Legion soldiers share the same freedoms, or lack of, as an American soldier.
Except I never drew a direct comparison between the US military and the Legion. I'm pointing out the fact that there are problems inherent within every military. The United States is supposed to be one of the most civilized nations ever created, but it still has such huge problems in its military. The Legion is made up of tribals and raiders with no education and a completely different set of moralities, and its military reflects that. If a modern civilization cannot create a military that meets the standards and moralities of that society, why would you expect a civilization made up of uneducated bronze age people living in a post apocalyptic world to be able to create a military that even comes close to meeting modern day moralities? Heck, if anything, Caesar's military stays true to their moral philosophies while our military does not stay true to the moral philosophies of our culture.
As for the "few" bad apples from the US military. That's clearly not the case. The system itself is full of problems. As I mentioned before, 25% of female military personnel reporting sixual harassment, that is not a small problem and it does not account for all the incidents that do not get reported. The Pat Tillman incident where a friendly fire incident was covered up and then used as propaganda was not the only such incident. Then there's the time when Rumsfeld said that the Department of Defense couldn't track over $2 trillion in transactions after an audit.
In the Legion, there are soldiers, and then there are slaves. So, I imagine, the image of the Legion as it's presented in NV is pretty accurate, accross the board. It really depends on how much freedom and leeway they give their slaves, which is never really elaborated on. Though, I doubt it's much.
I think it's probably safe to say that Caesar isn't the effective ruler of the Legion, so much as a figurehead. Even House will declare that killing Caesar has changed the current situation very little. He's a collection of proverbs for the Legion to quote to one another - nothing more.
Why would you assume that the Legion's depiction in NV is representative of all of the Legion? That's like saying the US troops fighting in Germany during WW2 is an accurate depiction of what the people in the rest of the United States are like.