United States Imperialism

Is the United States or has the United States ever been imperialistic?

Yes...

1.) The United States controlled the Philippines following the Treaty of Paris in 1898. The Philippine-American War that followed is also evidence of American imperialism. The Philippines became a colony in the fashion of Europe's New Imperialism.

2.) Intervention in Iraq is arguably imperialistic and the way we have fought for democracy in the middle east is borderline ethnocentric.

3.) The United States government's treatment of the Native American population was very racist and designed to remold them into a people more appropriately conformed to imperial desires.

No...

1.) Following the earthquakes in Haiti, America chose to not fly the flag at the Port-au-Prince Airport. In the words of President Obama, "we are not here as an occupation force, but as an international partner committed to supporting the government of Haiti on the road to recovery."
http://www.usatoday.com/news/world/2010-03-14-haiti-flag-flap_N.htm

2.) America is a part of the United Nations.

3.) American occupation of a territory, for example Japan, is only for a short period of time and for the benefit of the occupied country.