There is what is widely considered to be a "neutral" accent in American English, it is generally taught in broadcasting school/training. This could be what people mean when they say they "don't have an accent".
Not to speak for Oddtail, but I think what he means is something similar to what Margaret Atwood (she of 'Handmaiden's Tale'-fame) meant when she wrote that little essay about the 'one-way mirror' along the US-Canada border.
That when the Canadians look south, they see Americans, but when Americans look north, they see only reflections of themselves.
The noses of a great many Canadians resemble Porky Pig’s. This comes from spending so much time pressing them against the longest undefended one-way mirror in the world. The Canadians looking through this mirror behave the way people on the hidden side of such mirrors usually do: They observe, analyze, ponder, snoop and wonder what all the activity on the other side means in decipherable human terms.
The Americans, bless their innocent little hearts, are rarely aware that they are even being watched, much less by the Canadians. They just go on doing body language, playing in the sandbox of the world, bashing one another on the head and planning how to blow things up, same as always. If they think about Canada at all, it’s only when things get a bit snowy, or the water goes off, or the Canadians start fussing over some piddly detail, such as fish. Then they regard them as unpatriotic; for Americans don’t really see Canadians as foreigners, not like the Mexicans, unless they do something weird like speak French or beat the New York Yankees at baseball. Really, think the Americans, the Canadians are just like us, or would be if they could.
"Through the one-way mirror", Margaret Atwood, 1984
Thing is - it's not only the Canucks anymore feeling like that. It's basically anyone whose lives have been shaped to a not-insignificant degree by the process called 'Englishization' (and the US becoming 'the sole remaining superpower'). Of course, we on the other side of the one-way mirror come from vastly different places, with vastly different degrees of privilege - but at the core, there's an experience that a white MAWG from Germany shares with people from India, exchange students from China or my former office-mate from Kamerun: And that's being
'not-default in the eyes of America' - or more polite, but no less vexing:
'Default in the eyes of America when we're reallyreally not'.
And yes, it does feel exactly like that - Americans
do tend to speak as if they instinctively assumed they are the default, and that everybody else is just the same, except maybe for a regrettable fact of their having to run to catch up so they, too, can
"get with the program already" (And yes, 'Merricans abroad actually
do say that line. And no, it's not just the pinky-skinned ones).
And it's
a lot of 'you' - to varying degrees - even admirably ethical and painstakingly considerate folk like IICIH (sorry for making an example of you, IICIH)
It's OK, we still like you - Why do you think we spend non-negligible shares of our free time seeking out conversations with 'you guys'? And it's not like it's your fault being shaped by the place you were born into, just like we all were. It's just ... yeah, it
is 'a thing' - and 'the thing' in this our world and these our times is that there's lots of places, and then there's America.
[Edit: And no, I don't think it's the same thing as 'American Exceptionalism' - rather something adjacent. And no, this isn't an accusation or a 'you have to change your ways' or anything. It just ... is.]P.S.: Come to think of it: You, SnS, are probably the 'worst' example of an American to tell this to -> I have yet to see you write something that even remotely smacks of your assuming yourself to be the default, in any meaning of the word. Just coincidence, hope I didn't overstep my bounds.