Probably trivial because they adopted the tech later and it was easier. The last to modernize, will be the most modern. The US rolls out new tech and charges for it, and at this point charges and fees have been there since the start and there is no reason to remove them. There are banks that will pay the fees, so effectively a free transfer, but it is up to the consumer to select these companies to do business with. It is the old voting with the wallet method.

What is "most other countries"? As far as I'm aware, at least in the Eurozone ATMs also have fees (unless it's the same bank) and bank wires (SEPA) aren't instant either.

Operating ATMs may be "trivial", but it costs money, so why would you serve your competitor's customers cash for free?

Obviously it varies between counties, but here in the UK I can transfer money between my three banks essentially instantly (normally less than 15 seconds), for free. And we were late to the game. The only time I pay to use an ATM is at ones in small corner ships. Bank ones are almost always free, and you can use any bank's machine.

Planet Money did a good episode on why the US system is so bad compared to most other developed countries. Mostly seems to come down to the huge number of small bank's you have, it massively complicates any attempt to roll out a new tech platform.

Most ATMs don't charge a fee, so if your bank doesn't charge one for a withdrawal out of network, you're good. A lot of countries have had pretty good online banking offerings for a while now and free withdrawals at any ATM are typical.

SEPA is over 10 years old now, and while not the fastest protocol, modern banks clear transfers in a couple of hours. Not bad for something that allows you to wire money to some 500 million people. And the newer SCT instant payment scheme is being rolled out as we speak.

Fees in ATMs around Europe are rarely as extortionate as they are in the US

Sepa is not instant but it's miles ahead of ACH