/u/enter_matrix

I think you are already familiar with my post on this thread so let's use that as a starting point. I think this is a very good question, but I know for sure what's not fair: to lump all of SE Asia into one case of "catalyst" versus "cause". The reason is as follows. The degree of success in independence movements varied greatly.

At the outbreak of WW2, the Philippines was already in a Commonwealth of the US, with clear political support both domestic and in the US itself, for independence. In Vietnam, it was quite far away from independence, even if there were already independence movements. In Malaya, there were significant infighting among the aristocratic states, so it's difficult to assess whether they would have moved toward independence if there were no WW2. Surely, the form is very likely to be different than the Malaya we knew from history. It had consisted of the Federated States, Unfederated States, and Straits Settlements, all with very different realities of governance and influence under the British. Finally, in the Dutch East Indies one can argue that despite some independence movements, the Dutch colonials were quite effective in suppressing nationalist movements.

Because of all that, in many countries there were distinct differences in nationalism before and after WW2. So you can see the nature and development of nationalism in these states varied greatly. For more detail, consider Anthony Reid's Nationalism and Political Identity in SE Asia, 2010, which covers today's Indonesia, Malaysia, Singapore, Brunei; it does not cover Vietnam nor The Philippines. Anne Booth's Colonial Legacies, 2007, compares SE Asian countries (incl. all of the above) from the perspective of governance and economic potential.