Many credit union deposit accounts with ATM access can use some foreign ATMs with no fees and reasonable forex rates. Some online deposit accounts with ATM fee reimbursements will also reimburse foreign ATM fees and have reasonable forex rates. Things like Schwab and Fidelity, IIRC. My personal experience is a bit dated, but I'd try to have two separate cards on different networks if possible, because my ATM card only worked in half of the UK ATMs I tried, and that wasn't very convenient, as the ATMs I couldn't used were at the chunnel station and I needed cash for an unlicensed taxi.
Some people advise sticking with four-digit PINs for compatibility with older ATMs [1] but I don’t know if that’s a practical limitation at this point.
[1]: https://www.latimes.com/travel/deals/la-tr-spot-20140713-sto...
There are plenty of debit cards that you can use at foreign atm's with no ATM fee or foreign transaction fee.
The terms & conditions on my credit card sound like it should work (I shouldn’t be charged interest if I have a credit balance), but I’ve never tried it.
Failing that idea, do you have any tips for frequent American travellers on how to get foreign cash without paying excessive conversion fees?