You don't need to understand the language to laugh. Videos didn't always have sound, you know.

Do they ever dress up as cowboys and pilgrims and wear everyday clothes and form groups for people obsessed with American culture?

They had better.

I imagine they might. You never know, there could be an Oriental version of 'suna who keeps telling everyone to watch subs instead of dubs

Well I do know that the toy nerds show up at conventions and pay upwards of 50 bucks US for American Transformers and Halo figures.