American tourists (or maybe just all tourists in general) can be pretty excited about everything that is going on around them. The sights and experiences are new and exciting, and it's hard for them to contain their applause. You shouldn't be too surprised if you see American tourists clapping a bit excessively at things that most others would not consider clap-worthy. But can you really blame or judge them? They are just excited!
There is something so pure and cute about seeing tourists excited to visit a new place. After all, it is just pure enthusiasm.