I'm not even sure the americans have a GaN fighter radar optional, though others might know more on the subject.
They do, though just one and relatively rare type(An/apg-79v4 on remaining USMC F-18C/Ds;
not US NAVY E/F/Gs!).
I'm a bit sceptical about Russia having GaN even now, even if China can help with TRM production. We shall see though.
The biggest problem with Su-57 is it's slow production rate, i guess we can't expect Russia to crank them up in J-20 or F-35 numbers, but still merely two or even three dozen Su-57s a year for VKS would be very welcome.
VKS modern fighter strength is just not that big, and ironically Su-57s already form very noticeable portion of that number.
Don't treat VKS in same size league as USAF/PLAAF, they're more of a ~USN sized fighter force. Current production tempo, which is ~1.5 dozens including export, is solid for given force levels, for an expensive aircraft which isn't meant to replace rest of the force. More so entire sukhoi force, which also covers strike aircraft and entirely separate naval aviation branch.
Current TAF force design is clearly su-57 guiding 4++ assets; imminent future procurement priority is VLO LW(s-70), as well as apparently su-57 twin seater, able to exploit them better.
There's relatively wide expectation that VKS seats in "wait and see" position, looking if Sukhoi can deliver S-75 as a next gen LFI on a plate(and vise versa, Sukhoi bets that AF will bite), and they're looking at each other like two gangsters: who'll blink first.
This aircraft does show promise to go for full order in affordable budget, and it'll also likely be able to keep Russia competitive enough in air domain.