A complete and utter restructuring of all social and national norms and values was a very difficult process.
1. Such a Westernization as you describe, that a society "completely" and "utterly" restructures its "all" social and national norms, has never happened up to the present day.
2. Previously you were given just a popup once the Westernization is complete, with no explanations on what went on. Now you're told more: you're told that you modernized the military to the Western standard. Westernization in this game is a pure military reform.
Such a military reform to reorganize an army in a European model was widely attempted, some failed, some succeeded. AFAIK, Russia, Ottoman Empire and Persia all attempted by 18th century, and the Plain Indian adaptation of horses and guns could be counted into the list. Further down in the line, by 19th century, most of East Asia will follow, not only Japan.
If Westernization is to change, then the rest of the world needs to be balanced before that. The current advantage that the Western tech group has over the rest of the world is completely ludicrous and unrealistic. The gap in the unit types gets impossibly large, it's as if they're projecting 19th century imperialism retrospectively back into 17th when the gap wasn't that horrible. Japanese were able to successfully copy the musket technology from Portuguese by 16th century; Korea had Dutchmen in advisory positions in weapon manufacturing and military training in the capital in 17th century; Qing had access to European cannons at the same time, etc.
Not only the tech, also the numbers are completely wrong, that I still remember my Gujarat, which held the entirety of India AND Persia, still had less manpower and force limit compared to France. Seriously, all of the Indian subcontinent cannot provide more soldiers than France? Even if it can be somehow justified that the Western military technology was still absolutely superior over Asian that a 30K vs 30K battle should result in stackwipe on Asian with 152 men dying on Western side, it makes no sense that China or India fields less soldiers than any European nation. So, not only the tech/unit type is unfair, even the numbers are in favor of the Western Europe in a way defies justification.
My point?
The game doesn't make historical sense at all. This is a freaking video game, and all "arguments from history" that I've seen on this forum are purely selective. In my very humble opinion, 98% of historical arguments on this forum have been utter bullshit reflecting the poster's own biases rather than historical truths, and further ruining gameplay balance based on selective evidence is unacceptable.