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Let's Encrypt bans certificate usage by residents of US-sanctioned countries [pdf]
(letsencrypt.org)
For true stories that are so ridiculous, that you could have sworn it was an !theonion worthy story.
It's much easier said than done. Anyone can start a new Certificate Authority but for it to be useful internationally it (its public key) needs to be built-in to (trusted by) all of the popular web browsers, the largest of which are all controlled by US companies.
While that's absolutely a consideration, it's hardly an insurmountable issue.