It is American. In the UK, we'd write 11th March 2021. But I don't mind too much when it's non-ambiguous like this.
Is that also how you’d say it? If verbally asked what tomorrow is would you say “twenty seven February” or “twenty seventh February” or “twenty seventh of February”? Americans normally would say “February twenty seventh”.
Yes.
The 27th, or the 27th of February.
To us, US English seems to skip a lot of the small joining words of various flavours.
Well you're actually saying "the 27th day of the month of February" and removing some of the small joining words of various flavors. :) /s
I’m not going to comment on the author, though I will acknowledge the abrasive, unhealthy attitude.
Anyway, no. I don’t think there’s a clear “American” standard. Maybe there once was, but I’d just see a pile of numbers these days. It’s hostile to the consumer as it inherently leaves some uncertainty of how it should be consumed.
I will say, and maybe this is American - but I don’t think it is - that I often see dates formatted unambiguously as, e.g. March 11, 2021.