No doubt a tanker or an AWACs might be a tempting target,,,,, but you've got to get closer than you want to, and the US will vigorously defend those assets, so I just don't get all this "hoopla", at least we do have tankers, and we have AWAC's. The J-20's will have to come from somewhere, and they have to "show up somewhere in order to launch weapons at our assets??Well "weakness" in as much as any air force has tankers and early warning aircraft that can be targeted for destruction. I have no doubt they will be well-protected, but certainly they will not be impervious to attack, and somewhere in between "vulnerable" and "impervious" is where the J-20 comes in.
Its not a complicated picture if you are on alert, and we really have no idea how effective anyone's stealth is or isn't except our own. With our own 5th gens running a screen, and powerful radars overlapping coverage??? So granted these aircraft are very capable, and possibly L/O, that just makes defense a little tougher!
The J-20 is a land based aircraft, it does not have the mobility of the F-35B or F-35C, or for that matter the F-35A, or F-22 which may meet those tankers anywhere over a vast expanse of territory???