From my experience, I can tell you that non-native English english teachers generally have a standard accent(not kearalite or terrible arab accents). Secondly, their grammar is unbeatable.

An Arab can never develop a good accent(not even the standard one) unless they learn English as a first language in kindergarten. I assume you are not in Kindergarten!

Brits from the north have a brouge(an accent which is loathed world-wide, even by Brits from London). Texans also have an awful accent.

Point is there are variations even in the British and American accents. It all depends on their district/state than their nationality.