I agree you used chauvinistic to mean that, but you then followed it up by saying that you didn't have to justify why what they said is wrong. You do. It's also not the case that what they said was definitionally chauvinistic, although I'll let that slide because it was something similar enough.

Suppose it was the case that one nation was in every way better than all other countries. Shouldn't the citizens of that country be proud of that? Beyond pride, shouldn't they do everything they can to spread their glorious system to the world and bring prosperity to all? That doesn't necessarily mean wars and colonialism, that simply means all soft power efforts to implement systems that show themselves to work. I think the answer to this hypothetical is this nations citizens should feel pride and should spread their system.

The key point here is the United States isn't better than every country in the world, thus Americans shouldn't feel such extreme pride about their country. However, the United States is pretty good. I think some form of pride / patriotism are justified for Americans and even forms of soft power to implement effective policies are justified, but this answer is impossible to reach when you throw out all feel good thoughts about nations as chauvinistic.

This user seems to think the US superior to all other countries

I said no such thing.