I recall reading this as well. He loved the movie "The Last Pictue Show" so, it make sense. James Dean also filmed "Giant" in Dallas, so this may have been of interest to him.
My theory that these visits to the US in the 70s may have had something to do with research with these books he was writing. As to how he got the money, he may have raised some of it from temp jobs but, I've read that he does have relatives in the US so, that may have paid his way. Not sure what part of the country they may have resided.
I suspected New Jersey, but that's northeast.