I'm certain that the sale was OKed by the Pentagon. Foreign military sales always come with transfer restrictions. The Patriots have limited ballistic missile defense capability against "Scud like" and cruise missile threats. They are nearly worthless agains ICBM's.
It would be next to impossible for Spain to maintain the system in good condition without technical and material assistance from the U.S., in any event.
I found it pretty amusing reading a report of how an Indian military delegation was upset that the US was only offering them older PAC-2 missiles instead of the advanced PAC-3 variant.The US had last year pressurised Israel from selling it's Arrow missile system to India ,which the Indian military wanted to integrate with the Russian S-300 ,which it already operates in limited numbers.The irony is that the PAC-3 has been offered to Slammic states like Egypt & Saudi Arabia.