How did European Imperialism affect American Politics?

I'd suggest
that European imperialism played a significant role in shaping American politics. Consider the
Monroe Doctrine, as well as the Roosevelt Corollary to the Monroe Doctrine. One of the
fundamental cornerstones of American foreign policy was shaped as a response to European
influence in the Americas. Of course, it must be recognized that, during the early decades of
the 1800's, the United States lacked the military strength to actually enforce this foreign
policy claim, but the statement remained, by which the United States claimed in the Americas its
own sphere of influence.

In addition, we should consider America's own
imperialist adventures, beginning in the late 1800's. A critical moment in this history was the
Spanish-American War, where the United States acquired overseas possessions from Spain. Consider
also the Open Door Policy, through which the United States attempted to gain access to China
(which was then divided into European zones of influence). Additionally, we can mention numerous
US interventions in Latin America, as well as the construction of the Panama Canal (which was
itself only guaranteed by a US military intervention in Panama's revolution against Colombia).
Be aware that the United States has its own very real history of imperialism to contend
with.