1. Hitler was a Austrian man (I know he led Nazi Germany). He was originally a very arrogant individual (And became one again after WW1) seeing himself as far superior to others. He excelled in subjects interesting him. The subjects that didn't interest him were in fact worse. He was a madman, and sickly as well... He took many drugs that ruined his psyche. Funny thing too was that he was a terrible strategist..
2. His character is undoubtedly very charismatic. His ability to inspire others and rally support is unmistakably useful. He was a bit arrogant, and thought he was way more physically attractive than everyone else. Moreover, his strategem is terrible. (Worse than me in Company of Heroes 2[Kidding, I'm pretty good])
3. The United States should've dealt with him more. A shame that the USA did not notice the holocaust in the beginning stages, but a myriad of factors did prevent this knowledge from reaching the world... The USA would bring justice like they did Saddam Hussein. They should, and they would.