I understand it is easier for brits to do American accents than vice versa. But he does a good job. One of the worse accent sI heard by a black actor is Denzel in Mighty Quinn. Great actor bad accent
A lot have been imitating American movies since they were young
So imagine if you had been imitating Monty Python and you want to go into acting it'd or you'd be more receptive to it
Also we talk more laxed for the most part
But there are definitely laxed British accents we could definitely do.