I have no idea. Nobody here works for Apple since this is a user to user forum. Read the links on all the things you have to do to set up Apple Pay. Very likely one thing would be to change your country settings to the USA. Maybe then it might appear, but your problems may still not be over. For a temporary visit this might have ramifications you will not like such as having to cancel all your subscriptions and setting your apple ID balance to zero to be able to change country settings. Then you would likely need to make sure your card billing address matches the one you set for here in the USA. The Apple Pay Cash works through one of the USA banks and you have to meet US banking requirements to use that part of the service.
Note that this is also against Apple's terms and conditions since this is not your country of residency.
Read how to "Change your Apple ID country or region" click here --> https://support.apple.com/HT201389
The sections below are copied from the USA Apple Media Services Terms and Conditions document but I suspect they are very similar for all versions of this document --> https://www.apple.com/legal/internet-services/itunes/us/terms.html - Last Updated: September 16, 2020
"Our Services are available for your use in your country of residence (“Home Country”). By creating an account for use of the Services in a particular country or territory you are specifying it as your Home Country."