The USA doesn't want to deliver the F-35s because they are afraid that the Russians might use the S-400s in Turkey to collect data about the F-35s.
That is what they say but clearly that is a lie.
If they feared F-35s flying near S-400s and the Russians collecting critical data about the F-35 from the S-400s radars then they would ban Israel from using their F-35s in Syria... which they have not.
The fact that Israeli F-35s don't enter Syrian airspace and launch standoff attacks from bordering countries suggests the F-35 can't get past Syrian S-300s, let alone Russian S-400s.
Equally the US should jump at the chance of testing their downgraded export F-35s they sell to Turkey against the downgraded export S-400s Russia sold to Turkey and assess how effective the F-35 would be in real combat against the system.
The fact that they don't want a real world test means they know the end result... the F-35 is not worth the money and even their versions and the versions they sell to israel can't penetrate airspace defended by S-400s reliably.
You would think Russia would refuse to sell their powerful AD SAM system to Turkey, but they sold S-300V missiles and Tunguska SPAAG and missile vehicles to the west in the mid 1990s and after 30 years western SAMs and AD has not improved.
So there is no solution for now.
Bully the bully... tell the US to stick its F-35 programme where the sun does not shine. And suggest that US military bases and nuclear weapons will need to be removed from Turkish territory if you want to impose sanctions. Having Turkey is rather more valuable to HATO than it is to Turkey. Russia is not interested in invading Turkey or any HATO country, but HATO seems to be playing chicken with them and you can only poke the bear so many times before you lose your arm.
How often does Russia or India or China bully Turkey into doing things against their interests... Turkey should pick better friends.
Poland or Turkey is the first NATO member that will voluntary leave this genocidal Mafia.
I would guess Hungary is more likely to leave... and to leave the EU as well, who are strong arming them into become liberal freaks too.