I can't speak to the parent commenter's precise meaning, but I interpreted them to mean they oppose the current domestic and foreign policy of US political and business leadership (a distinction that blurs to the point of indistinguishability of late, courtesy of said domestic policy).
I believe that many Americans that were previously dismissive or ambivalent regarding critiques of US activity at home and abroad (either due to patriotism, realpolitik apologia, or general naïveté) are now re-evaluating some of the beliefs they hold about their country in light of the chronic political dysfunction and an absolutely breathtaking extent of corruption being perpetrated in broad daylight today (as well as indications that extensive corruption has long festered among our elite class, surfaced via the Epstein revelations).
Yea but if they just oppose the current administration isn't that just being anti-Trump instead of anti-American? His administration is just some other administration that'll come and go like foul sewage gas. We've had 47 of them. Does the OP become pro-America when their party is in charge or when certain conditions are met?
I don't know, just asking.
But I know that in my own upbringing I've always viewed America as a place where, because it's a democracy, we are never going to all be aligned or on the same page about policy direction. Even when I disagree with the Biden Administration or the Trump Administration on some number of issues, and believe my I've got a lot of those issues with the current one, I wouldn't think of myself as anti-American or wishing harm to the country. But that's just my own experience.