I'm in the US but both Venmo and Zelle are "currently not available in your country or region" in the App Store?

Hi,

I am currently working in the US for a few months, and have a US cellphone number on my work-issue iPhone, with AT&T being the provider. I also have a Swiss cellphone number on my private iPhone.

I have been trying to install Venmo and/or Zelle on the US iPhone, but in the App Store I get a message saying that both apps are "currently not available in your country".

I guess this is because I am somehow handcuffed to the Swiss AppleID even on the US phone. I read the Apple support information about changing the AppleID's country, but I'm concerned that if I change on the US phone I'm going to mess up all the apps, including subscribed services, that I already have on the Swiss phone, and cloud data. And that I want to keep them, because I'll be going back to Switzerland.

Is there a way to unbundle my AppleID from one phone without killing off the stuff in the other phone? Or, better still, a way to set up Venmo and/or Zelle without having to change the country of my AppleID?