japan and the US both use around 100-120 volts, so power adapters work in both countries. Can confirm because I have a famicom with the original power supply and it works just fine.
I was low-key on the TadaKatai ship, I'm starting to see the beauty of it.
Also is it not normal to do that with plugs or is this some region joke I don't get since I don't travel outside of the Philippines?
Electronics will work in both Japan and the US depending on where in Japan you live. US helped rebuild the south of Japan and Britain and France did the north after WW2. The difference is the frequency of the AC. 60 hz is the American standard while in Europe it's 50
Japan uses both 200V and 100V AC. Tokyo has the 200V 50Hz system.
Either way the USA uses 100V 60Hz. The console would be undervolt, but the Wii U should have a modern switching power supply and should work.