China and Taiwan is a domestic issue stemming from civil war, which you'd know if you ever picked up a history book. There's a reason Taiwan's current territorial claims are larger than the entirety of mainland China's (China signed some treaty with Vietnam, which Taiwan does not recognize).

China doesn’t typically intervene in clearly foreign affairs unless Chinese citizens are harmed

Two Chinese nationals killed while fleeing Taiwanese Coast Guard

“The Department of State fully recognizes that it may be necessary at some stage for the United States to take military action if [Taiwan] is to be denied to the communists… Such intervention should be publicly based not on obvious American strategic interests but on principles which are likely to have support in the international community, mainly the principle of self-determination of the [Taiwanese] people” — “Memorandum by the Acting Secretary of State to President Truman”

Not only do the majority of Taiwanese people not want independence from China [*], but less than a dozen UN countries even recognize Taiwan as a legitimate separate country from China, and none the legitimate ruler of China (ROC over PRC) as they would like--Taiwan’s airline is China Airlines, Taiwan’s banking is China Trust, Taiwan’s oil is China Petroleum, Taiwan’s communications are China Telecom; Taiwan speaks Chinese and has the same dialect as across the strait, Taiwan’s streets are named after mainland cities (unlike Hong Kong), the “local cuisine” is Chinese cuisine (and Taiwan competes in the Olympics as “Chinese Taipei”).

In 1971, the United Nations (General Assembly Resolution 2758) revoked recognition of Chiang Kai-shek’s ROC due to the KMT not being in governance (decreeing to “expel forthwith the representatives of Chiang Kai-shek from the place which they unlawfully occupy”) and recognized Taiwan as Chinese (not “two Chinas” or “one China, one Taiwan” to quote the session). The United Nations officially states that they “[consider] ‘Taiwan’ as a province of China with no separate status”, that “authorities in ‘Taipei’ are not considered to... enjoy any form of government status”, and that they “[consider] ‘Taiwan’ for all purposes to be an integral part of the People’s Republic of China.”

In 1972, the U.S. officially stated, “The United States acknowledges that all Chinese on either side of the Taiwan Strait maintain there is but one China and that Taiwan is a part of China. The United States Government does not challenge that position. It reaffirms its interest in a peaceful settlement of the Taiwan question by the Chinese themselves.” They STILL do not officially recognize Taiwan as separate from China.

[*] "臺灣民眾統獨立場趨勢分佈", conducted by Taiwan's National Chengchi University, an explicitly anti-CPC source, in 2022, showed the following results with regards to the perspective of Taiwanese citizens on independence and reunification: (Status Quo as Autonomous Part of China and Complete Unification Compiled [part of PRC] : 63.4%) (General Support for Independence Including Status Quo Moving Towards Independence [not part of PRC]: 30.3%) (Non-Response: 6.3%)

Even if you believe that Taiwan is "foreign" to the PRC, it is objectively not "clearly foreign."

Damn bro, good point. You should go tell the ROC marine corps that they have a map of a foreign country on their official emblem. What a wacky oversight nobody has noticed for half a century!

Taiwan is a conflict between china and Taiwan, so not clearly a foreign affair in my opinion. But I think also, that Taiwan is it’s own state and China should stop harassing Taiwan.