I'm using a US-Canada plan, my phone number is from Canada. When I'm in US, I can't get any verification code message, like adding credit card to my apple wallet or so...
@RaynaWang have you confirmed that all other services are working in the US, especially texting out and in? We have had other customers inquire about getting banking or other verification codes when travelling abroad and for many of them they have had to contact their banks to arrange other temporary options like receiving the code through email
