Radio friendly country music has been explicitly propaganda since the days of George W Bush. When they stopped playing Garth Brooks, Reba, the Dixie Chicks, etc. Dixie Chicks really were the big, loud turning point but it was earlier than them.
I really wish an experienced documentary maker would tackle the subject because it feels so, so heavily coordinated. Right wing political operatives co-opted country music the same way they did the churches before.