True, Huawei grows very fast, but it will take quite a good time for them to penetrate the US market, and dethrone apple, heck not dethrone but to become a major rival.
As for Mate 9 is underrated, i mainly meant by that, that it's undersold primary because the name isn't dominating as Samsung, as a result, given the price range of the device, it doesn't sell very good and those who are tech savy like us, will choose the best device that fits us, and i bet most of us will go for the Mate 9.
So far, all the 2017 flagship are not an upgrade over the M9, even downgrade at some regards
Price is one thing. But while a number of us on the forums are capable and willing to pay outright, many aren't. And while you can finance the mate 9, it is more difficult than iPhones or Galaxy devices. Which is of course because it isn't sold by any carrier. The vast majority of people in the USA buy from carriers or carrier authorized retailers like best buy. IMO, until they move to carriers, which should be soon based on rumors, then they don't be able to really compete in the USA on equal footing with Apple and Samsung.