We’ve been booking our US car hire through BAH for the last 10 years and never had an issue as Spouse/Partners are covered in the US, not just California:

https://www.avis.com/en/help/usa-faqs/additional-driver

Was made aware of this by a Preferred desk agent in Dallas back in 2016 having queued to add my wife.

I second the Preferred advice; it saves so much time. The latest version of the App is good, allowing you to browse alternative vehicles and swap out your allocation if you so choose. In certain locations it also supports express exit, so you get a QR code in the App and scan it at the exit barrier which automatically lets you out- no human interaction at all. Last month at SFO, from getting off the train at the consolidated car rental facility to hitting the highway took literally 5 minutes- brilliant!