" If yu have a strong regional accent, you may be best sticking to songs from your own region, "
Don't think this is necessary if you are able to modulate your accent - most people are.
If it was something you had to worry about, you would give up singing altogether - nearly all the Liverpool songs I know are sea songs .
I still have a reasonably recognisable Liverpool accent with hints of Mancunian, London and now Irish thrown in.
If I talk my sisters in Liverpool on the phone my wife will invariably say, "you're talking to the twins", - my accent noticeably changes.
What an good actor does in my opinion - is not to aim for a specific accent, but a general, say, neutral Scots or Irish one, and adapts it to be comprehensible to an audience.
I suppose there aren't any hard and fast rules about accents; if you cam handle a song in an accent and make it work for you and the audience (without giving offence) - why not - I can't so I don't.
I'm surprised nobody has mentioned the MacColl myth of making a rule that you must sing songs from your own region.
When Alan Lomax came to Britain in the 1950s he found the scene was ful of wannabe Woodies and Huddies and all the American stars of the time, including Ewan and Bert Lloyd (still have a recording of Ewan's 'Sixteen Tons'.
The great BBC mopping-up project had not long taken place and Lomax berated them, pointing out that if all those wonderful songs weren't sung they would die.
Ewan and Bert became born-again English speakers and insisted that the resident of his club should sing songs from their own country (not region) in accents as near to their own as possible - it's all written up somewhere.
Ewan was lucky - his home environment was Scots so, while by that time he was speaking in a middle-of-the road English accent, he has his home environment to fall back on.
He had a panic attack when Dylan came on the scene because he thought they might lose all the ground they's gained from the early days - hence the animosity.
I lived at their home for a month and spent a fair amount of time with Betsy - I found her hard to understand, but when she and Ewan got together you might as well have been listening to radio Ulan Bator.