First, an obvious point, define "Great." Great in what way, for whom, be it person or class.
Second, say when it was great so we know what you'd want to return OUR nation to, from its past? Calvin Coolidge days, turn of the century when J.P. Morgan lived and led Wall Street then? Plessy v Ferguson, days? What?
At what point prior to your starting to feature that cap was the nation "Great?"
When and how did the nation cease being great, in the sense you'd want to restore?
Before we left Vietnam, and the way we left it?
When young men were drafted into war and the danger of early death?
When Reagan was elected and the way he altered ways and means in the nation?
Eisenhower years, while Roy Cohn was alive and active, what?
HUAC days?
KIssinger's prime, in Chile? Cheap oil?
Kennedy Camelot?
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What we see, is a structured ambiguity, which fits the present-day normal definitional confines of "disinformation," when standing alone and unexplained, un-fleshed out. A slogan, oozing ambiguity while sounding nice to some indiscriminate thinkers. A huckster's pitch, akin to "Step Right Up?"
_________UPDATE_________
Link.
Further link.