Just use the website www.americanmilestounitedmiles.com and you can transfer them and you even get a 5k miles bonus. Just Kidding- i wish it was that easy.

As mentioned you can use AA miles to get to SFO. No way that i know of to use AA miles to fly united or Jetblue. You can often book on Partners/Alliances of if you had MR or UR points, but that can be tricky.