They literally got invaded by USA.

Context. That was after they bombed Pearl Harbor and occupied the Philippines (which was a U.S colony at the time).

North Korea and China aren't even a threat to Japan.

North Korea kidnaps their citizens and violates their airspace by launching rockets at them unprovoked. China has made similar threats, especially by sending "fishing boats" into their territorial waters.

https://www.japantimes.co.jp/news/2020/10/26/national/chinese-boats-prime-japanese-fishing-area-rise-nearly-four-times-2019/

By the way, they [China] do this with all their neighbors. It's their way of being a passive aggressive douche.

Japan should kick out USA and develop nukes.

The use of nukes is very controversial, especially as they have two cities that are living examples of being destroyed. Outside of peaceful uses like Power Plants, I'm not sure if the Japanese would actually accept having live nukes on their soil.

Japan is the most cucked country

A country that homogenous is not cucked. Try Sweden or Canada, or hell, the U.S instead. At least there will be Japanese people in the future, whereas the U.S will become some mixed race abomination.