oh no, it's true. Punk started in the US. The sex pistols was a fast, savvy import for the reasons stated above. that didn't stop the fierce, enthusiastic embrace of Punk in the UK anyway; with Thatcher on board, they desperately needed it.
Yes, except: Thatcher came along later (elected in 1979)—the core British punk scene developed circa 1974-78 with bands like the Sex Pistols, The Clash, Siouxsie and the Banshees, The Stranglers, and so on. (Thatcher undoubtedly turbocharged things in the 80s, though.)
In Please Kill Me, there’s a story about someone bringing an early copy of Anarchy in the UK to CBGB and the New York punk rockers were both “this sounds like 3 years ago” and “well damn, they one upped us.” Brits repackaging American music is whole thing.