Wandering Minstrel forgot to mention the finger in the ear and singing through your nose.

And there's the problem (mentioned somewhere in the thread - I can't be arsed to look it up, so credit to whoever you are) that the songs are done in school, and taught to kids at an early age. And at that stage the songs become nursery rhymes and lose any relevance. Would you go on stage and sing "Baa baa black sheep"? Of course not. But in a foreign language, "Baa baa black sheep" might be perfectly acceptable as a folk song of that country. The most obvious examples of this are Waltzing Matilda and Molly Malone, and Streets of London is going the same way. Some Beatles songs (especially the more 'cheesy' ones like Yellow Submarine and Octopus's Garden) may already be there - every kiddy's songbook I've seen features Yellow Submarine.

It used (19th c) to be popular to say jigs were Irish and reels were Scottish, regardless of actual origin - I guess the same way you'd expect rap artists today to be black/coloured. So maybe that's pushed it along - Irish/English/Scottish music is more a style than a matter of where the song came from. A fiddle book I've got says that one of the reels in it was actually listed in a Victorian music book published in Scotland as an English reel, even though it sounds as Scottish as you like. Name escapes me ATM - I'll look it up.

Grab.