The US doesn't have any enemies within range of the Chinese jets and the US won't sell the F22 to anybody near china.
They are both techno-wank projects to make generals feel cool and to keep a few aerospace companies in business. It took a while but we have finally corrupted them to be just like us - and we did the chinese as well!
The US has plenty of allies within range of the J-20, for example Taiwan, Korea, Japan. If China was to fight any of these countries, and the US got involved, air combat between the J-20 and F-22 is quite likely.
> They are both techno-wank projects to make generals feel cool and to keep a few aerospace companies in business.
There's an element of truth in that, yes. But it's been axiomatic in warfare from about 1940 onwards that air superiority is really important in a ground or naval campaign. (So they aren't just useless toys.)
This is changing as UAVs and smart missiles take over roles currently performed by manned aircraft.
There are also battle groups with F-18s and AWACS planes and so on that are much nearer than the F22s in Hawaii.