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Consider the amount of train/ferry transit between London and Paris. That doesn't exist in the US. Rental car companies don't keep that much extra stock on hand, and really do not love renting cars for inter-state one-way journeys.
I categorically reject that getting from Atlanta to London with ATL nonoperational would be either faster or easier than getting from London to Atlanta with LHR nonoperational.
The airlines that redirected flights to Paris arranged buses to London.
An alternative reading to it 'being idiotic' is that it was clearly an exaggeration to prompt some critical thinking about the original claim.
And I can tell you, it might be theoretically in Google Maps land to do the journey in 6 hours, but IRL in this scenario it won't happen. Actual empirical evidence.
Unless you're in the movie Planes, Trains and Automobiles.
By the way, the snide remarks you add to the end to each of your comments may be better suited for a place like Reddit or TruthSocial. The community standards guidelines for HN can be found at the bottom of the page.
I live close enough to LHR to notice the replacement of Boeing/Airbus with Cessna/Pipers from local airfields in the sky today. I also regularly drive to and/from Paris.
It is a six hour drive. But ONLY if you have your car ready, have booked a crossing ahead of time (otherwise you might want to slap another half day on those times), make no stops, you don't end up in a queue at UK customs (1 hour+ not infrequent occurrance). Don't happen to have your car sitting at CDG waiting for you? You'll have to hire one, but you'll be unlikely to be able to take that to the UK so you're then finding somewhere to drop that off and somehow cross as a foot passenger which you can't do on Le Shuttle...
Point being, cross-border travel throws up all of these hurdles which you simply don't have in the US example.