It depends:


I arrived once from NRT on the SQ flight and had to stand in line at the immigration counters for about 2 hours!!Was very annoyed that LAX does not have fast track or special counter for F class pax that day
I was glad to have 4 hours transit before my conecting flight, many other pax in line with me had much tighter connections and many propably missed their flights

Some months later I arrived from AKL on NZ and was off the plane, through immigration, picked up luggage and through customs in less than 20 min!
Tried to standby for an earlier connecting flight but didn't work so had to spend 5 hours in the RCC.