There are places that do something like this in the states. It's not the same thing exactly, mind you, but there are things for children at amusement parks, local and state faires, as well as ren faires. Not to mention various community events. It all depends on where you live, in the end.
In any case, regardless of the type of event it is in real life it translates poorly into a video game. It's fine if they want to make an event based off of something like this but to make the player be a Mumor groupie where all you do is cheer on? Really?
The event wasn't exactly welcomed when it first came out. The year after people en mass were already kind of tired of it and by the third year well, it became "Really? This again? Lame SE... really, really lame and lazy."
The event is long due for a revamp. It's been done to death by now.
Keep in mind, I'd be saying something similar even if it wasn't Mumor we were talking about.
As I mentioned before, there is a lot of culture that SE can incorporate into this game as far as Summer Festivals in Japan are concerned. They don't have to fixate on Mumor only.