"Banana republic" implies more than what the dictionary definition is. If you look at the wealth distribution in any example "banana republic", you'll find a few very wealthy people/warlords and many dirt poor with close to nothing in between
Calling the US a “banana republic” is a shocking headline, which I think is the real point. The US economy is not very similar to actual banana republics though. There are some aspects which are becoming similar, yes, but also many in which they’re not.
To me it reads as a clickbait headline.
I think that any argument that needs the dictionary to be wrong, is probably wrong.