I'm not ashamed of the United States past. Compared to other countries and what they were doing at the time, Americans were acting like choir boys.
Germany, Japan, Great Britain, France, Russia, Spain and others were all building Empires. They weren't shy about busting heads to do it either.
Consider England's colonization of India. Russia's building of the trans-Siberian rail road. Japan's occupation of Korea and parts of China. Spain's brutal repression in Cuba and the Philippines. France's actions in North Africa and Indo-China.
All of that was before Germany's two world wars. The chaos that occurred before and after both of them.
Don't get me started on Stalin, Mao or Pol Pot.
Are we perfect? No. Are we a cut above the competition? Hell yeah.