They’d allow for serving more direct (point to point) routes than trains as the infrastructure cost is so much lower than laying and maintaining tracks. Rail serving high volume routes still makes sense, especially while electric plans remain relatively small.
The solution is not aircraft, the solution is more and better trains. Or perhaps autonomous buses/trucks depending on how far out you look.
That leaves most of Asia outside India/China/Korea/Japan, and pretty much all of Australia/Oceania, Africa, the Middle East, and the entire New World.
I would love to see high-speed rail take over the world, but there's a lot of sparsely-populated places out there, and it makes sense to investigate technologies to support them.
In the US it'd require similar effort/cost as the Interstate Highway System did, but would probably yield equal economic benefit.
In general aircraft for passenger or cargo routes take a few routes and don't shift much.
The basic logic is two-fold:
First, it's much faster, cheaper, and less contentious to create new routes, and capacity can quickly be switched (even seasonally or in response to events) thanks to neither needing to pay for nor lay tracks.
Secondly, it shortens a lot of journeys. Even in countries with pretty extensive rail infrastructure it is common to combine two or more trips via "hub" cities in order to complete a journey. This adds time because you travel further and have to change trains and wait around. The difference could be particularly extreme given that only longer distance intercity trains tend to be high speed, and electric planes will eventually be faster even than high speed rail.
A similar change happened with long haul air travel: as twin engine planes have been able to fly further over water due to safety improvements, the traiditional hub model has lost out as many more point-to-point international routes were created.
While I think they might re-shape regional transport in some pretty important ways, electric planes won't replace high speed rail (and kerosene burning jets) on more popular routes, at least not for a while (and perhaps, debatably, never). Trains are incredibly efficient and hard to beat when you need to regularly move a lot of people, and electric aircraft, while they're about to become useful, are going to remain relatively small and range limited for quite a while.
"Somewhat"? The energy density needs to get better by a factor of like, an order of magnitude to be competitive.
And it's still going to require human pilots for at least 10 years even aside from that.