Democracy is a great thing, but it's a lot more nuisanced when it is more of a buzzword right now than an idea or system to be uphold. It appears that the US doesn't really care about democracy, at least not as much it pretend it does. The arms sales has been going on for decades, under both Republicans and Democrats. It never had been all about democracy, the US doesn't want Taiwan to declare independce because it doesn't want to involve itself in the issue unless it's absolutely necessary, it also doesn't want China to forcefully annex it so it offers it a certain degree of protection, in the same time, the US recognize the reality that China is a much bigger market and a lot more influential on the world stage compared to Taiwan, therefore it yield to the "one China policy" so it can have a formal relationship with the PRC. It's has always been more about strategic balance between Taiwan and China than Democracy. The recent "messages" to China isn't much of a policy shift. The U.S has always been a bit of two faced regarding China and Taiwan, it stands in the way of China to annex it's "rouge province" but in the same time it also doesn't offer enough protection and support towards Taiwan for it's formal independence. In other words, the U.S is against BOTH sides' interests by protecting the status quo.
Trump made the phrase "America first" popular, but in reality it has always been America's rule of the thumb for foreign policies. Democracy is a side product at best ,and sometimes it goes terribly wrong and further distablizes the involved country/region. It doesn't take a genius to see through the hypocrisy and irony of America condemning various regimes for their human right violations, but in the same time it ignores Saudi Arabia's bombardment of Yemen with the weapons it sold to them.
It's super naive to assume any foreign policy decisions as a humanitarian act, they are usually about more control over the region and more profit. Countries don't go after each other for ideologies, they go after their own interests.