If only ROC won the mainland and was not USA ally, I think the question would have been put to rest long ago.
I think HK are hyper nationalistic to the terms of Chinese in comparison to mainland and Taiwan counterparts. Could be a result of the fact that the previous colonizers were not Chinese. Although there is an adversion to non-Cantonese or HK Cantonese speakers, there is no movement to declare themselves non-Chinese.
Could be the a factor that the Cantonese in the region in have immigrated to many different States and see no threat to their Tang culture.
On Taiwan there is almost no pride in being Chinese. It was a liability under Japanese rule. It is a liability under Green rule. Minnan speakers on Taiwan are hyper-patroitic to the point that if another Minnan speaker has dual citizenship, they are not considered Taiwanese.
Of course this issue is not easily resolved since the government under Green leadership has been pushing the Taiwanese-Chinese survey every year.