All dialects randomly conserve and innovate on features. And when a dialect is split off by, in those case, geography, they will start to conserve and innovate different features. And it's true that American English conserved rhoticity which was lost in most of England, but it did innovate e.g. /æ/-raising where British English conserved the original pronunciation. But that's just two of many more features, and neither geographical region clearly conserved more than the other.
Saying that there are no intelligible reasons for any feature change of a language in any dialect, (i.e. that they are all random) is a strong claim.
In mainstream linguistics sound changes are assumed to be random. Some are more common than others of course, but there's no saying what sound change will happen in English next.
https://www.bbc.com/culture/article/20180207-how-americans-p...
The last time this came up on HN, the comment thread already disagreed on whether "mention" should be spelled "menchin", "menshin", "menchun", or "menshun".
a spelling reform cud[] keep “mention” and still significantly improov the orthography wer it to simply aply the rules more consistently. And when wurds ar genuinely different, like “ask/aask” or “uv/ov” it's not going to hurt to spell them differently.
[] although how to spell put/putt is an open question. here I have sided with northerners and decided to spell them the same.
[As an aside, why did you drop the doubled "p" from "apply" but not the doubled "f" from "different" or the doubled "l" from "spell"?]