The official policy is that the US wants a peaceful solution.
While the US is clearly leaning towards Taiwan, the current situation is very comfortable for the US.
For continued support, the US can pull that card whenever it wishes. Taiwan continues to be valuable when it comes to negotiations with China as well. So the best thing for the US would be if the current situation continued.
I think that if China becomes a more valuable ally in the future, Taiwan would be negotiable.
As for the governments - the Chinese government today is quite similar to Taiwan's government 25 years ago. Neither country has had a nice history.
Out of a neocon perspective, backing Taiwan will only be profitable for 20 to 25 years more. After that, China will be depending on either USA or Canada for food, if the current population growth continues. Then, of course, supporting China taking over Taiwan would be more profitable for the US.
While typing this I just realized that I have committed myself to living in Taiwan. Should probably stock up on canned food and ammo...
