Yes, all of which could be done in hours less time than it would take to get from Atlanta to any comparable airport.

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.