There's an interesting attitude towards the word "nationalism" in US. As you say, it's probably one of the most enthusiastically civic nationalist nation in the world - indeed, to the point where American sociologists have described it as a "civic religion" at times. But the word "nationalism" itself is almost exclusively interpreted as "ethnic nationalism", and has an unambiguously negative vibe. So people who practice civic nationalism describe themselves as "patriots" instead.

We actually had elected officials chanting “USA! USA!” at the last State of the Union Address.

Very fine people on all sides of course.

My favorite part of the "USA! USA!" chant is how seriously non-Americans are about it. Every time I've started or participated in a "USA! USA!" chant it was only about 15% nationalism and 85% a joke. Part of its enchanting humor is how that seems lost on everybody else.

"We are what we pretend to be, so we must be careful about what we pretend to be."

So part of why it’s “funny” is that it’s offensive to most people who don’t find it funny?

I must admit, you’re the first person I’ve ever heard refer to a USA chant as enchanting.