The subject doesn’t deserve a serious answer so I gave it a mocking one.
If you really, really, really want a serious beat-down, though, I’m happy to oblige.
The entire history of language is that of words changing, dropping, and accruing meanings. You could make the argument that every person uses every word with a slightly different connotation than everyone else, and no doubt there’s a book that says exactly that.
That’s both the curse and the wonderfulness of language. Words are so flexible that they can capture the infinite complexity of an ever-changing world yet have a reservoir of core truth that makes them understood by most people most of the time.
And yet words can be abused. Politically correct as a term has no meaning at all these days; it’s devolved into an all-purpose attack on anything anybody doesn’t like, the dirty hippie of our day. Obama is regularly called a Fascist Communist, a ridiculous oxymoron. Creationists and climate deniers misuse the words of science quite deliberately to shore up arguments that have no real basis in fact. It’s not just meaning that gets abused. Illiterate’s place apostrophe’s into plural’s at a furious clip.
Maybe at some point in the future, society will break down sufficiently that plural’s can rightly be spelled with an apostrophe. That’s very unlikely, though. There is too much pushback from good writers to overcome. Good writers, and all those who are concerned about the language and the trend toward appropriating words for propaganda, will continue to push back with all their strength and scorn. Politically correct has been lost but Fascist Communist is still a signal of derangement.
And banana republic as an all-purpose term for the United States being anything other than the number one nation in the world in every conceivable way is still in the latter category. It signals ignorance rather than derangement at this point, but it has potential. The U.S. cannot become a true banana republic under any faintly plausible scenario. It cannot even become a metaphorical banana republic under any faintly plausible scenario. If China were to beat U.S. GDP - likely in the semi-near future - the U.S. would still have four times the per capita GDP of China, making even saying that it is number 2 a stretch. It will not and can not become a banana republic, even if a thousand blog posts call it that. They will merely become an additional thousand on top of the millions of already silly, ignorant, and eminently forgettable blog posts on the net.
And if you quote them approvingly, you will continue to earn the scorn of everybody who truly understands history, economics, politics, and words. Your choice.