Maybe people should start condensing the 'Metro Detroit Area' as the MDA (or something like that) similar to the way the 'Greater Toronto Area' is labeled the GTA.
I don't know how many people outside of Toronto (or Canada) know what GTA means. (I know that I didn't). Abbreviations that make sense locally rarely resonate globally.
As someone that grew up a few hours from Toronto, I'd be confident in saying that the GTA is in the common vernacular for most folks in Southern Ontario. I agree that those outside of that area (in Canada at least) wouldn't, since from outside it looks like it's all Toronto.
For people here inside the region this is actually common to say Metro area or SE MI it is just difficult for people outside or who have never been. They just say Detroit. In fact, when I am away on travel, I will tell people I am originally from Lansing and they simply say "so Detroit?" and I def wouldnt consider Lansing part of the MDA