If your inbound flight is on time and you're flying J, I'd give you good odds of making the flight. If you end up missing the connection, TK will rebook you. Unfortunately, the SFO flight is one of the latest US-bound flights to leave IST so you'd likely not make it back to SFO the same day. Worst case they'd put you up in a hotel and put you on the same nonstop the following day, so really it depends on how urgently you need to be in SFO.

Since it's a protected connection I'd keep it, personally.