I live in Canada but travel to the States and when I do I put in my American SIM card which of course has a different phone number. Sometimes when in the States I get locked out of my account and it sends a verification code to my Canadian number, but I don't really want to put the SIM card back in the phone just to get the code. Is there any way I can have the verification code go to both numbers simultaneously.
If you have another phone, you can forward both phone calls and messages from one number to another. If you have another iPhone, you can forward messages for free - just go to Settings > Messages > Text Message Forwarding. This will make the message appear on both devices within a minute or so of each other. If you don't have an iPhone, I expect other phones would have an SMS forwarding capability, but there would be a per message cost.
I use this so I don't have to carry a work and personal phone, and it works well. The only complication you have is that it is in 2 different countries, so there will be roaming charges (I expect).