If there was one, who’d follow it? York, New York, Melbourne (Ireland) and Melbourne (Australia) all have their variants from what London speaks.
To the latter point, for example, a lot of companies use Oxford comma in general but don't for press releases and related because AP doesn't follow Oxford.
In general, though, it all works out. I see very little appetite for another group of authorities than the ones who already exist.
You might be interested in "Because Internet: Understanding the New Rules of Language" by Gretchen McCulloch. McCulloch is a linguist, but it's a light/layperson's book. I really enjoyed it.
This is, by the way, not a criticism of your use of “Americans”, which I and all English speakers use the same way.