Not trying to get into a political or ideological argument here. Are we part of the US? Yes. Do I have a US passport? Again yes. Unfortunately, the are many instances for which we are considered US residents and many others for which we are not. That's the way it is for us.
I've never applied for a Citi CC before so I can only give you an example of my experience with AMEX so you can at least understand my concern. I've had my eye on the Blue Cash Preferred and the PRG for a long time. Both of these cards have the US gas stations, US supermakets, etc. categories. I've called AMEX three times with the same question I posted here (Is PR considered part of the US?) and I have received three different answers: US categories DON'T apply to PR, US categories DO apply to PR and the best one was that only merchants in military facilities are considered part of the US for these categories. Needless to say, I haven't applied for those cards.
I just don't want to waste a credit pull to later get the "Sorry, US means only the 50 states and DC" switcheroo.