Just to set the record straight. only Agnetha, Benny & Bjorn are Swedish born and breed. Anni-Frid is the product of a German soldier and a Norwegian woman during World War II. Whether this was a love match or a child of Hitler’s “let’s rape woman to get more Aryan babies” program is debated. Her mother died young, her grandmother moved to Sweden and raised her there, and her father came out of the woodwork after Frida got rich and famous in ABBA.
Shane MacGowan was born in England.
Fleetwood Mac is a complicated case, but I initially saw them as an American band from California (because of Lindsey Buckingham and Stevie Nicks) that happened to have some Brits. Later, I found that the band had a whole other, entirely British identity and output for a decade before Buckingham and Nicks joined.