That SFO flight is pretty solid on ‘on time’ - SFO customs is quicker than LAX and a much smaller airport (and less hectic than LAX). It does come in around the same time as flights from Asia and the Middle East, so depending on those flights, that’s where you can experience a bottleneck in customs.

You can get to United < 20 mins from international terminal. SFO international terminal is small, but effective. Baggage reclaim is quick and just behind customs. United terminal is kinda lame for a hub, fyi it’s carpeted in case you have a wheelie bag…