“But over time, the executive branch grew exceedingly powerful. Two world wars emphasized the president’s commander in chief role and removed constraints on its power. By the second half of the 20th century, the republic was routinely fighting wars without its legislative branch, Congress, declaring war, as the Constitution required. With Congress often paralyzed by political conflict, presidents increasingly governed by edicts.”
You are conflating civilization with empire, the two words have different definitions for a reason. Imperialism is, according to Miriam-Webster, ‘the policy, practice, or advocacy of extending the power and dominion of a nation especially by direct territorial acquisitions or by gaining indirect control over the political or economic life of other areas’. New Zealand qualifies as civilization in most peoples’ books, it’s not an empire, and there are lots of other similar examples out there.