"David is more than just a football player and I think he does extremely well to give football here a lift," said Gullit.
"But I doubt if they really want that. I think they are afraid of football because it's so popular everywhere around the world. I think they will just control it so it doesn't become more popular than their American sports.
"So it is very hard for him (Beckham)," added Gullit.
"They will never allow that, and in some ways I can understand it as well.
"I have my doubts if they really want to make it popular. Some sports already have had a bit of a dive so they don't want American football to become less popular, or basketball or baseball."
Gullit, a former World and European Player of the Year who previously coached Chelsea, Newcastle United and Feyenoord, had said he was ready for "a huge challenge" after being appointed Galaxy head coach last November.
Just nine months later, though, Gullit resigned for personal reasons with the team struggling to book a place in the end-of-season play-offs.
Asked if he had any regrets in accepting the Galaxy position, Gullit replied: "Of course you do, especially if you know what you know now. I don't know if I would have taken the same decision again, that's for sure."