As a non native English speaker, the hardest to understand are people from England. The easiest to understand are people from the NL. The most comfortable to work with: germans, italians, spaniards… since they make the same grammar mistakes I make (so we all understand our mistakes)
American here...always thought the NL/Dutch accent was weirdly the most American-like accent? Which I assume is universally fairly easy to understand because of all the media content? I've been around Dutch natives before where it took surprisingly long before realizing they weren't from the US.
In my opinion the Scottish accent is the most difficult accent to understand.
"Introduced" the Scottish accent via Youtube to some Mexican co-workers who are fluent English speakers and they freaked out. Will never forget one saying "WTF is this? How can this possibly be real?". Guy generally thought it was some sort of fake prank way of speaking and couldn't grasp that people actually spoke like that.
I'm American and concur with this. Aside from some slightly accented tweaks here and there, the Dutch speak a remarkably clear and rhotic English that feels quite comfortable to listen to.
It's odd because Dutch itself, being a Germanic language, has a lot of pronunciation commonality with the most conservative of all English accents, Scottish. You can hear it in this video, where a sentence composed of common Germanic words is spoken in every Germanic language:
The Dutch accent is closest to the American; if you didn't know English or Dutch, you would be hard pressed to tell the two apart. They sound a lot alike from a distance.
If it weren't for Trainspotting, which I adore, I'd be utterly useless at understanding Scots accents. As it is, I can just barely manage.
A coworker told me some years ago that understanding my broken English was easy for him, as he had worked extensively with other Spaniards and my grammar and pronunciation was just like them :)
Honestly, I'm regularly surprised by how nice and patient people from everywhere are, paying attention to my words even if my English is not, even today, as good as I would like it to be. Including French people. Including British people.
