Does the DOT rule regarding free 24hr cancellation apply to non-US fllghts?

As we know, DOT rule allows a free 24hr cancellation for a purchased flight, as long as it is purchased more than seven days in advance. My understanding was that it only applied to US-originated or US-bound flights.

However there seem to be nothing in 14 CFR 259.5 limiting this to US-related flights; the plain reading of rules seems to be that ANY flight (such as domestic flight Mumbai-Delhi) is covered, as long as the carrier itself is "covered carrier" under 14 CFR 259. And a "covered carrier" is any airline, which "operates to, from or within the United States".

QUESTION: Is this correct understanding that if an airline has any flights to or from USA, all their flights must offer free 24hr cancellation (if purchased more than 7 days before flight), even if those flights do not originate, connect or terminate in the USA?

And, if you know, does the flight need to be purchased from the USA to be eligible, or it could be purchased, for example, from India?

PS. I called Delta to check, and they confirmed they offer free 24hr cancellation on a NRT-PVG flight (which flies from Tokyo to Shanghai and is Delta-operated). However Delta is a US-based airline; I wonder whether anyone had experience with airlines like China Eastern or Air India, which are not US-based.

Note: this question is not about Orbitz/Expedia which offer 24hr free cancellation on almost all flights, including those airlines which don't fly to USA.