But even if the F/A-XX is going to match the notional 3000km range of the larger land-based NGAD, it doesn't change the balance of power.
At the very most, the US Navy could have 3 deployed carriers (aka floating airbases) at a distance of 3000km.
But China should be able to control the air at that distance, because it can field a larger force of J-36.
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Given that the J-36 is already flying, that implies it will be in service ahead of NGAD or F/A-XX.
At the same time, we'll probably see China "outspending" the US in arms race and building more 6th gen aircraft.
If you ignore the undervalued exchange rate controlled by the Chinese government, then in terms of actual output of goods and services, the Washington-based World Bank purchasing power parity numbers suggest the Chinese economy is actually 25% larger than the US economy.
And if you correct for measurement differences (such imputed rent in the US and the undercounting of Chinese consumption figures), the indications are the Chinese economy is somewhere between 50-100% larger than the US.
If they're still planning on operating NGAD from the Second Island Chain, it doesn't matter how expensive or no-compromise the NGAD is. Nor does it really matter how many NGADs are built.
Let's say there is a better NGAD and they concentrate enough to retain local air superiority around Guam, the limitation is still the number of airbases. Those airbases and their runways will still be under attack, which means more aircraft will be trapped on the ground, unable to takeoff and therefore vulnerable to follow on attacks.
And trying to operate an Air Dominance aircraft from the Third Island Chain will require something bigger than the B-21. Even if technologically feasible, the cost is going to be unaffordable. NGAD at $300 Mn is already being called unaffordable, and the B-21 is $800 Mn