Originally Posted by mikew99

But the U.S. does have control over tickets sold in the U.S. It's the ticket purchase the U.S. DOT rule applies to; the journey itself is irrelevant.

So as not to derail this thread with a discussion that is likely off topic, I'll point to a prior discussion of the U.S. DOT 24-hour reservation requirement, which also contains links to the official U.S. DOT rule, so you may read it for yourself.