Most banks require you to phone in to change your PIN or go in branch. It would be nice to change the PIN from what Monzo has provided.
Calling in requires interacting with a robot who asks you to choose a PIN using the a push-tone telephone.
Changing PIN at an ATM is not a thing in the land of the free 
, UK Monzonauts. As such there is no method to change the PIN at all.
Wait you can’t even change it at the ATM.
The land of ATM charges, you must be 21 to do anything and can I see your ID.
Well there is no need to change it at a physical terminals.
Retitled thread as there is no ability to choose or change a PIN with US cards.
Thanks for the great feedback - you can now change your PIN in the app! In the “Manage” tab for your card, tap “Change my PIN”. 
edit: if you don’t see this in your app yet, we’re slowly rolling this out to customers. 