well , F14s combat results in USAF were disappointing . F14 needed extensive maintenance to be usefull and It was hard to do in combat situation and in carrier , so USA put it aside and they have better fighters to do the role ( F18 for this example ) ... their F15 is ruling skies without even losing a single battle and they already developed F22 , so putting aside F14 couldn't have any negative impact on their air force ( also , it decreased cost of maintenance , training and .... ) ...I dont know if F14 retirement was due to what you are saying (stopping Iran's ways to get spare parts and components of such a powerful platform) or simply that the wheel of Military Indrustrial Complex had to be turning and turning, draining resources and resources of the american taxpayers in a never-ending-story, so USA decided to change a mighty high-tech platform for a less mighty platform (Hornets/SuperHornets) only to favour the Military Ind. Complex ethernal hunger, not for technical reasons.
Also it's important to note USA decided to favour SuperHornets instead of building an even more powerful Tomcat platform, the SuperTomcat, which would have been a decades long air dominant plane.
F14 era is already over , Iran simply doesn't have any replacement for its useless fleet or else we wouldn't operate these old fighters in 2020s , this is bitter truth , other things are excuses ...