Okay, I've got Mull of Kintyre up on youtube. Nice bagpipes. I can see why this would not take off over here in the US. Maybe I'm Amazed it's not. Biggest seller of the 70's? It would have to be the UK.
Here are two opposing opinions on YouTube:
nukeim2000 (3 months ago) Show Hide 0 
WTF , ok i am a huge beatle fan , love wings and all the beatles solo stuff esp George Harrison , but this is in my opinion (and its myn) that this is the worst tune put out by any beatle! Oh blah de oh blah da is better
MonsieurMal (20 hours ago)
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no, mate this is such a great song, if you go to the mull of kintyre you will understand why he wrote this song