There is quite a bit of complexity in the American system. I mean, it's quite well organized, but there are some things you have to be aware of.
American Military RanksThat's the complete list. For the most part, the ranks are equal between most the branches. You will most likely not see an O-10 (four star) or higher (five star) unless it is during a time of conflict or war.
This is a list of the currently active highest commanders int he US military, most of them being on the Joint Chiefs of Staff. Marine Corps Generals are almost unheard of. You are more likely to obtain these high ranks while in the Air Force or Navy at least that's my understanding.
This is a list of the highest ranking commanders the United States has ever had, with George Washington being the highest of them all, of course. I love military history and when it comes to the rank system, I always love to talk about it and examine how it works and the complexities and organization behind it.