What technology prevents a american helicopter from being shot down by a russian anti aircraft missile?
The open question is rather, if the S-500 system can beat the F35 stealth capabilities (nobody know that as far as I know as it was never tried). Not that russians systems are useless against ordinary planes and helicopters.
You prevent enemy air defenses from shooting down your aircraft by blowing them up as part of SEAD/DEAD missions, which is exactly what the US did.
How do you think operations like these are executed? One helicopter just enters Venezuelan air space and hopes for the best?