It takes 10-12 minutes at the most to walk between the farthest gates at T4 and the Tom Bradley International Terminal (also known as TBIT or Terminal B).

If you were to misconnect, you should be protected on a later flight; American has a flight to SYD departing at 11:15 pm and Qantas has a flight departing to BNE at 11:20 pm, where you can connect to SYD.