Yeah, that's an absurd claim.

Americans watch the same TV channels. They shop in the same national retailers. There are some small differences in regional cuisine, but burgers, pizza, tacos, fried chicken, etc. are common everywhere. The same musicians are popular everywhere. The same 4 sports are the popular ones everywhere.

There are regional festivals celebrated in Europe that have been celebrated since before Europeans set foot in the Americas. The regional foods are completely different. Even though football is the most popular sport in most places, the number 2 sport varies greatly. There are bands and singers that are popular across Europe, plus a lot of American cultural exports that are popular too. But there are lots of regional kinds of music that are popular within certain countries.

The fact that Mardi Gras in New Orleans is so popular shows just how homogenous the culture is. To Europeans, Mardi Gras is just a very typical American-style festival. And yet, it draws Americans from other states because it's considered to be so unique.