Thanks for the responses to my Why glam meant next to nothing in the US query.
Some further thoughts:
The UK has a tradition of camp theatricality from the music hall and the pantomime. It's often said that the average Englishman can't wait to drag up. This is reflected in The Kinks, Madness, the Smiths and many others who are quintessentially English in their approach (I know the Kinks enjoyed American success but not in their 'English' period of 1965-71 approx.) Perhaps this doesn't translate across the Atlantic beyond cult status. When I think of mainstream US rock of the early 70s names like Lynryd Sknyrnd and the Doobie Brothers spring to mind - music (I use the term loosely) and image as far away from The Sweet and Roxy Music as it's possible to get. Perhaps good old fashioned prejudice played a part whereby glam was seen as limey faggot music and not rawk.
Like punk a few years after, glam was reaction music - reaction against the grey and dreary 70s that was life in England, and also a reaction against the grey and dreary music of Pink Floyd, Yes etc. A generation gap was opening up in popular music in the UK where your big brother listened to prog rock and wore an ex-army greatcoat while your kid sister had pictures of Bolan on her bedroom wall and wore glittery make-up.
To ask another question: Glam rock was teenage music. If glam meant next to nothing in the US what was a 13 year old listening to in Montana or Massachusetts in 1973? Did a specific teenage music still exist?