South Korea is possibly an example, one of the few, where imperialism (of both sides) was accompanied by good dose of pragmatism and great amount of luck. This is however not the usual result of US interventions. Germany and Japan are on this short list too - almost complete destruction was followed by great progress but I guess this is in big part also a way these societies were before anyway. They both did wrong and understood it afterward. Whenever the scene was not so clear US had messed up.
There were also examples where US military was used to satisfy explicit business needs if Smedley Butler were still around he could tell you something about that but then again if he lived in McCarthy era he would be revealed as a hidden commie and liberal or?
Corruption of US agents in 'introduction of democracy' and 'opening way to prosperity' in Iraq made a joke of the high moral ground that US wanted to have. We will never know for sure of course but chances are that US did a great disservice to people of Iraq and Syria by said corruption, associated lies etc. Were that not enough, genuine errors and plain incompetence and negligence helped the bloody mess to develop.
One thing that I cannot see trough is Ukraine. Both sides there are the same if looked at by not involved observer. The same corruption and incompetence which makes a question of US motives quite interesting - this clearly cannot be a case of informed, well meaning intervention as moral high ground does not really exists in Kiev. If so then it is either incompetence combined with naivety, evil conspiracy (NATO seems to be stronger already and some countries in the region are more willing to by US military HW now) or just accident. I'd actually preferred US to be involved in evil conspiracy here as a though of a global police force being so naive and/or incompetent is scary.
Independent on the motives of 'democracy' introducing troops, I would still run away if their arrival in my country were imminent. And to answer the question of imperialism - it certainly looks like it from aside. Pity your boys and girls and whole bunch of bystanders had to die in actions that look like imperial hegemony.