That's weird as for May 6 QR's website allows me to book DEL-DOH and DOH-SFO as two separate segments using multi-city option. Somehow doesn't allow me to book when selecting DEL-SFO.
Interestingly website does allow me to book MAA/BLR/BOM-SFO using one-way option (not multi-city).
Suggest HUCA and refer agent to website which shows flights available to book.
However important to note that official travel bubble rules don't allow transit via DOH to USA.