You can just have GV assign you a new number--you have to provide a number for a verification call at that time, but it doesn't have to be yours. Easiest for someone who travels to the US often is to set it up with whatever prepaid SIM you pick up. Once GV is set up, you can delete the forwarding number. If you have a friend or relative in the US, you can just use their number and delete it after setup.

If your number was assigned to you by GV, it comes from bandwidth.com's block of VoIP numbers. I suspect that the bank verification systems have a list of which exchanges belong to VoIP services and block them. My GV number started its life as an AT&T cell number and was ported in, so although it "belongs" to bandwidth.com now, the exchange is an AT&T exchange. I have friends who signed up for Fi for a cheap phone and ported to GV when they cancelled; their numbers also work fine, probably because those numbers originally come from T-Mobile.