Have you tried calling them and asking them if they could send to the US?
For many accounts people more usually order statements over the phone rather than going into the branch - obviously I don't know about yours.
Do you have an address in the UK registered with the bank that the statements could be picked up from?
Fiancée visa 2014 → FLR(M) Oct 2014 → FLR(M) Mar 2017 → SET(M) Sep 2019. I'm not one of the experts here - The only thing I know for sure is our story, so please double-check any advice I give!