Conversely, you could say the US has no real equivalent to the doujin scene.

WHY is even a physical Silicon Valley still necessary?

One could argue that the doujin way is a better launchpad for a wide variety of ideas than VC-funded startups:

People, especially young people including many females, create something from the comfort of their bedrooms, without any pressure (like many software/game devs of the 1980s), other people enjoy and even improve their products, and if they get popular enough then big companies may turn them into proper franchises.

Why doesn't the US foster that kind of environment more? Why does everything have to be a company with millions of dollars? In fact, most of the Western internet is actually hostile to young artists and developers..