You can log out of your US account in App Store, login with your other country account, download the app, then log out and log back in to your US account.
It will maintain authentication for some time and let you update the app, but eventually it expires. Then you get the sketchiest dialog box ever randomly when doing anything on your phone:
“If you have an Apple ID, enter the password”
What it actually means to say is, “I know you have another Apple ID that’s not currently logged in as primary, and I’m trying to background update apps owned by that account but the authentication expired. Please enter the password for [other Apple ID].”
It will maintain authentication for some time and let you update the app, but eventually it expires. Then you get the sketchiest dialog box ever randomly when doing anything on your phone:
“If you have an Apple ID, enter the password”
What it actually means to say is, “I know you have another Apple ID that’s not currently logged in as primary, and I’m trying to background update apps owned by that account but the authentication expired. Please enter the password for [other Apple ID].”