I want to say always has been but I can't recall for usage since it first appeared, but for a very long time, I would say it's associated with being white, and supporting a white dominated country. I mean, what is the Patriot Front?
en.wikipedia.org
They have the name right there and it was founded in 2017. I already said it, someone with a visible American flag is suspect to me, as I don't see what there is to be proud of about America, personally speaking, and in most cases, at least down here, right behind the America is a Trump flag.

Patriot Front - Wikipedia


Patriot Front
Patriot Front focuses on theatrical rhetoric and activism that can be easily distributed as propaganda for its chapters across the country.
www.splcenter.org
They have the name right there and it was founded in 2017. I already said it, someone with a visible American flag is suspect to me, as I don't see what there is to be proud of about America, personally speaking, and in most cases, at least down here, right behind the America is a Trump flag.