The way I see it for those that speak English we all have an accent of some kind myself included. I have no trouble understanding Americans but I do have trouble with my attention span when listening to Southern drawls.ZZZZZZ....
For actual understanding of English there are some accents in Yorkshire, Northumberland and Norfolk UK that I really have to pay attention to to understand.
Some Scottish too.
As regards Australia and New Zealand I wish they were closer too. Just too many hours flying time to get there. Easy to understand folks and down to earth.
Cheers, and I will sign off with an Americanism here, you all have a good day!
G.