Is 1h55m layover time enough for US pre clearance at Abu Dhabi?

You should be fine. Abu Dhabi is all one huge terminal connected internally. Transfer security and pre-clearance can sometimes be crowded and take a long time, but Etihad typically holds the departing flight in such cases to wait for people.

Because you clear immigration and customs in Abu Dhabi, the flight arrives into the U.S. as a domestic flight, so your checked bags will be transferred for you, and you do not need to reclear immigration or security. You will land in LAX at the Tom Bradly International Terminal (TBIT) and will depart from either TBIT, Terminal 4, Terminal 5, or the remote American Eagle terminal (gates 52A-52J). These terminals are connected airside, so it's important that you stay inside and do not exit to baggage claim or outside. When you get out of the plane in LAX, stay on the same floor (do not go down to baggage claim). Check the departure monitors to see the terminal and gate for your flight to SJC. If it is T4, follow the signs to gates 40-49. There are hallways and moving walkways between TBIT and T4. If it is T5, walk to T4 and then follow the signs for gates 50-59. If it is the American Eagle remote terminal (gates 52A-52J), walk to T4, go to gate 44, and take the escalator down to the gate, where a bus will take you to the remote terminal; there is no need to walk to T5.

My guess is that your LAX-SJC flight will depart from the remote American Eagle terminal (gates 52A-52J), so walk to T4 gate 44 and take the bus.