I suspect that Shatz's definition would be quite different from yours and mine.
What leftists (as well as the Buchananites) object to is a foreign policy defined by our national interest. Things like "freedom of the seas" and "ample supplies of energy" are in our national interest. But either motivation would be proclaimed as "imperialistic" by the left and the Brigadiers.
But the left would happily have us intervene on the basis of "humanitarian interests", even when based on a false premise -- as in Kosovo. Even when it served our national interests not one whit -- or actually worked against them.
At bottom, the left's anti-imperial impulse and objection to acting on behalf of our national interests is that, somehow, these interests are perceived to be primarily "commercial". Thus, connected to "profit" and, accordingly, possessed of some sort of evil corporate intent.
In this respect, I guess the left and the Brigadiers aren't that far apart...
Well, most of the Western States are colonies of Washington DC, but I guess that really doesn't count...
In reference to the US, its just so many words posing as thought.
The US does not rule any other country, nor does it force its will on anyone. The raw materials it needs it buys at market prices. The investments it makes overseas are made by private companies, not by the US government.
The soldiers it posts overseas defend the countries where they are posted, but do not interfere with the politics of the country itself.
In those cases where we intervene militarily, we withdraw when the fighting is over, and do not stick around to rule, even in cases where it might make sense to stick around.
In other words, there is no US empire.