When I take domestic flights within the US (between places like St. Louis, Denver, NYC, and LA), security takes far longer for several subtle reasons. Everyone has to show a government ID to a TSA employee (and get your photo checked against a database) before proceeding to the actual security lines. Then, most of the security lines use full-body scanners, not just metal detectors; some have moving parts and some don't, but they all require you to actually stand there for a second instead of just passing through. Every single person also has to take their shoes off before they go into those scanners, and you put your shoes through the same slower scanning system that the baggage goes through (which basically doubles the load and halves the bandwidth of the baggage conveyor belt).
In my experience, flying internationally out of/into the US (with both Japan and Canada as the other side) is no more security than flying domestically within the US. Which basically means we have full international-level security even for flying domestically here.
In a post-9/11 world, I took an airplane to university and back, and on a regular basis from [SMALL CITY] airport. I could, as a disorganized young adult, be at the airport within 10-15 before boarding time with luggage to check.
Pre-9/11, my family travelled internationally and it was always a 3+ hour, pack-a-lunch affair to be at [MAJOR CITY] airport.
You can tell it was pre-9/11 because you didn't need to throw the lunch away before getting to the part where you have to wait the longest.
But I've never had, like, a sandwich taken from me.
I took flights in the 2010's that didn't feel all that different from boarding a bus. You went to the desk to check in and to give them any checked baggage, walked to the waiting area to wait with a couple of dozen people, then went outside to board the plane. Any plane that would eventually connect to an international airport would have passengers go through security, but otherwise no.