It's not a monoculture, but there aren't many places on a typical tourist's itinerary that aren't also 3-5x the price of a European, Asian, South American, or Caribbean destination. It doesn't make US tourism bad, but at a 5x price differential one may weigh whether they want to see the Grand Canyon or Hawaii that much more than the Andes or Malta. There may be underappreciated gems in the US, but the fact that they are underappreciated also means they aren't popular destinations for mass tourism.