The relationship between the US and Taiwan is much more principally economic. Billions in economic trade on an annual basis between the US and Taiwan. Much, much more than what is spent on military systems for Taiwan.first of all, China would most likely NOT attack taiwan. China had never invaded a neighboring "state??" let alone a nation e.g Japan, Korea, Mongolia..etc. It is only natural for China to rearm itself because the relationship between Taiwan and United States has become almost strictly military reasons.
As to invading other "states" or nations, the PRC, in my lifetime, has in fact invaded all of the following nations for any number of their own reasons. India, Korea, Tibet, Vietnam...