Is there any common culture anymore? A product in a grocery store freezer is named after an inside joke from a sports media site that most sports fan problem don’t even know. That’s a market of a divided culture.
If you’re in a group of 20 Americans of different ages and backgrounds, it seems like it would be hard to make cultural references that everyone would understand. What are common movies, TV shows, and music that everyone knows?
Marvel puts out a few billion dollar films a year but I wouldn’t think more than maybe 15 people in that group would get a Thanos reference. There are so many shows that it’s unlikely everyone has seen the same ones or even knew about them. Music is all over the place.
That’s one reason social media is so popular. You can find people who like the same stuff you like much easier.