> This one seems to defy the rule.
No it doesn't. If I pronounce the "h", then using "an" sounds weird. If I don't, then "a" sounds weird.
> Journalists and films seem to use "an historic" with an American accent
Curious if you have a link to a video of this, I can't imagine it sounding correct.
I didn't know about "an historic" until I heard it from American journalists. They did pronounce the 'h' and it did indeed sound very wrong. I believe I first heard it from Rachel Maddow. I can't find any clips, but there are a bunch of transcripts from her show if you search up:
> Rachel Maddow "an historic day"
For example:
- https://www.nbcnews.com/id/wbna47356492
- https://www.ms.now/transcript/2013-11-21-msna738766