The title is simply wrong.
1) B-2, F-22, and F-35 can all be used to throw missiles at these sorts of targets and then exit the area. The HQ-9 / Patriot can't track stealth aircraft at extreme range effectively. Or you throw sea skimming / low altitude cruise missiles with jamming to provide EW cover.
http://nationalinterest.org/blog/the-buzz/american-f-22s-b-2...
> The Raptors “kick down the door” using their unique combination of stealth, high altitude and blistering speed to target the nodes of the integrated air defense system so that the B-2s can proceed to their targets unmolested. It’s a mission the F-22s have only gotten better at with the Increment 3.1 upgrade that allows the jet to geo-locate emitters much more precisely than before. And that capability will continue to improve with the Raptor’s forthcoming Increment 3.2B upgrade.
> The other option to take down an integrated air defense system is to use a combination of standoff weapons like the JASSM and JASSM-ER cruise missiles together with electronic attacks from a platform like the EA-18G Growler. The Growler can not only jam the enemy’s radar, but can generate an ellipse to target the missile site. The problem there is precisely updating the cruise missile with current track data before the enemy moves during the incoming weapons’ time of flight.
2) HQ-9 [if based on Patriot] is actually less effective than the modern Russian systems. Without the ability to move substantial distances, HQ-9 isn't a serious threat to the US. However, pretty much every US ally in the region isn't capable of standing up to that sort of thing. Given the region is largely divided into the US / Chinese spheres of influence at this point it doesn't really matter because there aren't neutral parties.
3) I'm honestly more concerned about China sparking a major war than I am about their ability to create no-fly zones.
------
EDIT:
Since I'm rate limited:
Realistically, whether you realize or it, China is in that position and has been for 20 years.
A missile base in Hainan would have the range to hit anything transiting to Vietnam via the sea. Short of taking Hainan away from China, Vietnam can be closed to ships by China at any time.
China isn't interested in provoking a military conflict but rather guaranteeing its security and a world position equal to the US in all theaters.
Similarly, its why Hainan has a semi-covert submarine base: