That happens any time I do that anywhere. It's not FDev's issue. On a couple of occasions I've had it happen elsewhere and realized I was checking out in euros / pounds rather than dollars.
It is sort of odd that some of the largest, richest financial institutions on earth (Citibank & Chase, who my credit cards are with) don't do it automatically. I can only assume it's down to U.S. regulations and not them.
It does sound very weird! I assume that you can pay in a foreign currency if you travel abroad..
Maybe worth contacting your bank in order to understand what the exact problem is.

Citibank foreign transaction fee — Here's what you need to know
Your full guide to Citibank's foreign transaction fees.