History. Current practice. Just because it is not reported on Faux or CNN doesn’t mean the US isn’t and hasn’t been doing it since shortly after 1776.
The US has for the last century or so operated on an “if you can’t steal it, break it” system. Readers can esily look up the dozens of countries the US has destabilized, attacked by proxy or outright invaded. Since Obama came to power promising to end the current wars and not start any new ones, we can hand him Iraq, Libya, Syria, Ukraine. If we include ongoing and new regime change/colour-revolutions, we have Egypt, Hong Kong, Venezuela plus a ton more in Africa.
Ya, no US imperialism. And 1 million military personnel scattered in 1,000 foreign bases. And then there’s the entire IMF/WTO/World Bank/US$-reserve-currency system that invades/cripples economies and dictates terms to sovereign countries. Thee is no need to show “proof” of imperialism, the US claims such rights regularly. Obama putting it all under the euphemism “indispensable nation”.
Empires have learned never admit to or call itself an Empire. But the US is by any reasonable definition, an empire.
“An empire is a geographically extensive group of diverse states and peoples (ethnic groups) united and ruled by a central authority, either by a monarch (emperor, empress) or an oligarchy.” The US just happens to elect its monarchy and political aristocracy which are controlled by the oligarchs.