US knows S-400 pretty well already.
Buying weapons from country which kills ur soldiers shows respect and backbone?
The S-400 is waste of money trash, yet do you believe that even without the purchase of it Turkey would have gotten the F-35s?
The purchase of it is just a dumb excuse to take Turkey out of the program, not to give us the planes we already paid for and to sanction us. We all know the real reasons why it all happened.