I don't know those other cultures as well as I do the American one. There is some infamous weirdness in Japanese pop culture, but I think that's more attributable to the failure of Japanese imperialism that ended with the humiliation of the atomic bomb drops.
Mass infantilization is hardly the human norm; what's normal, rather, is decadence or carefree, childish recklessness only in the upper reaches of a highly unequal society. Eastern cultures in particular haven't been plagued by monotheism and have been more grounded in pragmatic philosophies. China was dominated for centuries by a conservative form of secular humanism (Confucianism). India has had an eclectic outlook on all philosophies and religions, absorbing them into Hinduism. Japanese culture was shaped by an animistic worship of nature (Shinto), comparable to Daoism, and by Buddhism.
Those religions have their flaws in my view, but they're far more responsible and mature than exoteric Christianity, since the latter religion lost the plot. From the beginning, the younger, American society was inspired by babyish individualism, by the desire to practice heretical forms of Christianity without being reined in by the old world Church. That idolizing of personal liberties grew into consumerism, although American culture was tempered by some pragmatism, respect for hard work, and tragic paranoia, due to the harsh experience of the pioneers on the lawless frontier.
Personal freedoms made the US a leader in innovation, which in turn made some American companies wealthy. The resulting boom-and-bust cycle of America's free-market capitalism turned the US into a virtual plutocracy, since the wealthy few had to control the democracy to secure their fortunes, by brainwashing the majority into overlooking the downtimes caused by the warped American version of capitalism.
That's where infantilization fits into the American context, so there were several conditions that laid the groundwork, including a hopeless, pie-in-the-sky religion (fundamentalist Christianity), individualism, and economic domination. Add to that the separation of North America from the old world's problems, by the oceans, which allowed the US to shape itself.
If some Eastern societies have likewise been infantilized, I'd expect that to have been due to Western influence, via the monoculture produced by globalization. If there are independent causes of the problem, I'm not aware of them, but as I said, I don't know those cultures as well.
