The problem with the US is that apparently we can never do anything right. If we hadn't gone into Iraq, people would be yelling at us for leaving an evil dictator in power. When we did, people yelled at us for not having a reason to go to war. We just can't win.
To answer the question though, NO the US is not a military empire. We do not use our military to take and hold territory so therefore we are not an empire. Haha.