I'm Muslim. Born in the US. I've seen politicians and right wing public figures call my entire faith anti-American. One of them just had a nice memorial for their one-year since their death.
The term may have had an agreed upon meaning at some point, but not anymore.
Edit: it seems like most right-wing people conflate "non-Christian" with "anti-American". i don't know what's worse; the fact that these people say and think it, or the fact that their constituents don't know the difference.
It doesn’t have to have an agreed upon meaning. My point is its not inherently bad to think something is anti-American.
In fact, treating the very idea of judging something as “anti-American” as inherently illegitimate is quite literally anti-American. Its saying Americans shouldn’t be allowed to have opinions about what their country stands for.