I think the US is overplaying their influence on HK. People in HK regularly protest (on the street, even) against Beijing's apparent interference in local politics or social matters such as education and elections. At the end of the day HK is part of China and this how they act towards Beijing. I don't think the US can waltz in to HK and apply their special brand of moral pressure for HK to 'do the right thing'...
I don't think HK cares that much about US relations. They can defer to China to help get their way if they need it for trade related matters. I don't think they will want to be seen as caving to US pressure here.
