The difference between being an "ally" of US or not only has to do with its current economic interests. Until recently China was viewed as a big friend. And the US only decided to do something against it when it became clear that China would not allow US companies to control their economy. In the list of US "friends" we see dictatorships like Saudi Arabia and Thailand, and countries with numerous human rights violations such as the Philippines. This is not a great track record for a country that purports to be the champion of democracy around the world.