This time we did online check in & bypassed the airline counter as we were traveling with carry on's only. We went straight to US Customs from our airline limo, It cut our time by about a half hour to 40 minutes.
In the past we usually arrived between two and a half hours & three hours. We scanned the line up to see if there was time to grab a coffee. Keep in mind that there will be line ups at the airline counter as people who didn't do online check in - check in or check baggage. Sometimes it's quick - other times all it takes is an issue with someone ahead of you to slow things right down. After the airline counter you go to US customs.
On our December trip we encountered the new kiosks for the first time. (things slow a bit as many need help with the system) After you enter your passport & info and get your print out you are directed to a customs line up by a staff member who reviews the print out. Some lines move faster then others... Then it's off to security, there is usually a bottle neck at this point. Depending on your travel date (March break, Easter, Weekend or weekday etc). 3 hours ahead may be needed.
I estimate it took us about an hour to 90 minutes in December from curb to departure lounge.. It was a mid morning on a Monday flight.