Japan has legal impediments for export of weapons, but this is not the case in Korea. Since they now have a very serious domestic fighter program of their own, it’s likely that this US tech would find it’s way into THEIR fighter, and then would be exported —in many cases in markets where the US is highly active.
So the US tax payer would be shelling-out TO BE PUT OUT OF BIZ.
And despite the amazing state of affairs on it’s Northern border, in many cases South Korea gives off signs that it views defense budget as simply an extension of an industrial policy —the weapons developed are not done with a mind to maximizing DEFENSE benefit, and instead other benefits.
In other words, they rely so heavily on deterrence by the USA that they take the risks SK faces less seriously than the US does.
This is historically unusual, unsustainable, and BIZARRE.