I think you're reading too much into the colonial versus non-colonial divide.
I think it's more accurate to use a vassal versus non-vassal distinction, because countries do have enough sovereignty to change their allegiances or to remain neutral. It may be painful but it is possible for the vast majority of countries.
An example of an exception would be somewhere like Bhutan, where India funds and trains the Bhutan Army and the Bhutan Police.
Bhutan has literally lost control of its internal and external sovereignty to India, which is the defacto colonial power.
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Anyway, so what we have is an international system where previously the USA was the largest actor from an economic and naval (trade) perspective. In the case of US/Japan, it was in the mutual interest to enter into a lord/vassal type relationship, where Japan was grandfathered/privileged into the existing system with the USA on top.
But now we have a situation where China has a larger economy than the USA in terms of actual output.
The National Science Foundation also reported that China was expected to pass the US in terms of technology R&D spending in 2018.
This means that China has the capacity to displace the USA in terms of economic attraction, especially to its neighbours in Asia.
China is also the world's largest trading nation and which sits at the centre of the Asian trading network.
That will still be the case even if Trump cuts off all US trade with China.
And historically, the world's largest trading nation builds the world's largest navy to protect its trade.
And the world's largest economy does have the resources to build such a navy.
So the existing US-led system is breaking down because of the Rise of China, and most countries in Asia don't want to get involved in a US-China competition, because they will suffer in the conflict and they don't know who will be the winner.
But in the coming decades, it should become obvious that China will come out on top of any military/economic conflict with the USA, and that China's neighbours would be better off aligning with China instead of the USA.
So as China continues to grow, it would be in China's interests to maintain the liberal trade/investment order, and also military freedom of navigation. Thereby replacing the US in the international order.
This is what is driving US-China tensions today
I think you're neglecting the nuance and driving power of colonialism and decolonization in an inaccurate attempt to simply focus on hard power.
The hard power of military and economic prowess are easy to claim to be quantifiable, and easy to misleadingly characterize as "lord-vassal" relationships.
However the soft power multipliers of hard power including propaganda, public perception, elite affinity, national or sub-national alignment, alliances and allegiances, are all heavily affected by historical and cultural factors strongly influenced by colonialism and decolonization.
It is indeed a "culture war" in the international arena today but it is not the "culture war" from the Western narrative which really refers to internal Western cultural evolution, but rather an evolution of the international system from one that is an oppressive Western oligarchy, with roots in the colonial era at this point in history dominated by the US, into one where other countries and cultures have more sway and more of the overall pie.