It is weird. I think it is in part because America is the first enlightenment nation. We have no blood or deep history binding us together, so superficial and melodramatic shows of solidarity become much more important in generating a stable sense social identity. Think of it as a bunch of deracinated individuals attempting to say "see, 'we' are a 'we'!"
The puritans were virtue-signallers par excellance, so that probably also flows through to what you see today.
What do you mean by "first enlightenment nation"? I haven't heard this before. I thought the ideas of the enlightenment were first in various European countries but I don't think that's what you mean?
My parse is, the USA is founded on documents and philosophy instead of the personal power of a string of hereditary leaders and/or their overthrowers. I also feel the comment ignores the nuance of the fact that France's claim to be "An" enlightenment nation, if France wanted to make such a claim, is not so different than that of the USA just because France might be on its 5th Republic. How long has the L/E/F motto been the motto of France or French citizens anyway? The other side of that nuance being that perhaps French nationalism has a different flavor because it could be about different forms of nation at different times.
I think it is fascinating that you see such symbolism in standing with hand over heart for the playing of the national anthem and also point to the disgust for players opting to kneel as a reason people are not watching football.
That's the symbolism they are invoking when they kneel! They do not want to show a solidarity that they do not believe exists. That people would give up watching football over it sort of supports their side of the argument.
The puritans were virtue-signallers par excellance, so that probably also flows through to what you see today.