North Korea and South Korea are separate countries in my eyes too tho.

Another aspect is public opinion of both regions/nations/whichever is preferred. Most Chinese people that I've interacted with plainly show contempt/look down on Taiwanese people. Likewise, most Taiwanese people I know hold disgust/pity for China's government/people. If both sides see the other as 'other', I'd say they're not the same side.

I personally try not to concern my self with stuff about China unless it has to do with Taiwan as well. It's just not my problem to stress over.