Edit, after checking wikipedia I see that at least according to it most of East Asia and some other bits and pieces use yyyymmdd, which I know at least programmers would love to be more common. I'd be happy to read answers dipping into the reasons for that too, but the title is the one I'm looking for.
Just to clarify, you need to be aware that the US is not consistent-- The US military, for example, always uses the dd.mm.yyyy format.
I'm not sure you need a historian for this? In East Asia (e.g. Chinese) you literally say "2017 year 9 month 25 day", in much of Europe (e.g. the UK) you literally say "the 25th of September 2017", and in the US you literally say "September 25th 2017". The written standards follow how people express the dates in the spoken language. Seems like more of a linguistics question.