Most Americans didn't even know what it was. Thousands of records were cut but got virtually no airtime on mainstream US radio, or anywhere else in the world. Northern English DJs discovered a neglected black American art form - in the days when there was no youtube to aid research - and brought it to the UK. It remained an underground scene throughout the 1970's, a youth culture spread by word of mouth, with virtually zero media exposure. The closest thing we had in the south at the time was the occasional DJ's filling dancefloors in places like the Mecca on Southampton pier with crossover hits by mainstream soul artists like Roberta Flack and Candi Staton, but none of the rare small label gems getting spun in places like Wigan and Stoke. Most people in the 1970s thought black American music meant Donna Summer. You're welcome
