Democracy tends to depend on Empire Building. The more democratic the US has become the more imperialist we have also become. This results in many of the problems we have were we look to nationalize more things to enable resources and power to be directed external.
Ryan Chapman has a great video on DEMOCRACY: From Antiquity to Modernity [1]
So the Spanish American war was not imperialistic...
Or the US controlling most of South America (Monroe Doctrine)...
How about taking control of most of North America from the First Nations through genocidal actions?
Your claim is not based in the actual history of the US, but instead viewing it through a politicized and simplistic lens.
Other than an incredible brief era at the start of the US, we've been imperialistic in our foreign policy.
Ryan Chapman has a great video on DEMOCRACY: From Antiquity to Modernity [1]
[1] https://www.youtube.com/watch?v=UplwT_a1IT8