When I first came to the US, I was amazed how different it from Europe, they look similar on TV, but when looking at it with your own eyes, thousands of tiny details reveal it.
And later, when I traveled in different US cities in several US states on both coasts, I was amazed, how different part of the US are like each other. It might sound funny, the but same style of light switches in places thousands of miles apart struck me. Let alone, similar street signs, similar pavement styles, similar police cars, similar fire trucks, star-spangled flags everywhere.
The US has cultural codes, the identity.
I would even say that the difference for example between the US and the UK is larger than the difference between the UK and France.
So, like it or not, but the US is a nation.