USAA bank not available on Garmin Pay is a missed opportunity given appeal of Garmin watches for military

I have 2 guesses as to what may be going on here. None of my cards worked (past tense: new Ultra owner) with Garmin Pay. 
Guess #1 has to do with a possible security issue where the banks are not satisfied with Garmin’s security protocols for either the watch itself or their mobile app. 
Guess #2 the Garmin install base may be too small for some banks to frankly care. Garmin should be reaching out to banks everywhere to solicit Garmin Pay. Isn’t there a department within Garmin that handles this side of the business?

It is the same with Navy Federal. They dont work with Garmin Pay and it is not Garmin's fault. For some reason USAA and NFCU chose not to work with it. I do agree it a shame though we need to point the finger properly here.

+1 on Garmin Pay support for USAA bank (if anyone out there happens to be counting votes...)

Until there's no agreement between your US bank and Garmin, you can use Curve card (I think this is available in the US) with Garmin Pay. Many users across multiple countries in the same shoes managed to circumnavigate the same issue by adding Curve card to their Garmin Pay and never looked back. I do use not only my bank card but Curve and Revolut cards as well with GP for multi currency availability. HTH