Having been thru something very similar to this, I definitely do not agree with you. About 10 years ago, after they started the watchlist system, I was returning to Chicago airport from Finland business trip. Got off plane, had 3 hours before my connecting flight. All I had to do was go thru customs and then wait.
Right when I got to the front of line, their system that checks watchlist failed at the NATIONAL level. Being IT, I wasn't initially concerned because everyone has some redundancy and backup processes in place, right? Not so fast. After standing in line for 3 hours, with now 1000 people in line behind me, I started getting irritated and asked them what backup plan they had in place in case system was not coming up. There was NONE, as far as they were concerned we could stand there with no food or water forever. To go to bathroom you lost your place in line. Since I had missed my flight already and had only 3 hours of sleep in last 24 hours, I left my place in line to get water and use bathroom, this was about 9pm at night. I laid down on bench in customs terminal and closed my eyes to rest. I woke up at 11pm to an empty terminal, sometime between 9-11 the system came up. So luckily I got a 1 way rental car and drove to Green Bay, arriving home at 2:30am, with no luggage of course. How I stayed awake during that drive I still don't know.
Now here is the good part: The system that crashed only dealt with domestic passengers, not people from other countries with Visa's. This really nice lady from Denmark I sat next to on plane went right thru customs with no issues, only people from USA were stuck.
Now don't tell me you needed the system for security purposes. I had my drivers license, my intinery showed I left a week ago for Finland and was returning home. A mental midget could figure out I was not a terrorist, along with everyone else in line. The government was just too damn incompetent to have ANY plan in place in case that system was offline. Were all these people supposed to starve to death (there is no food court in customs terminal where you get off) in the name of national security? The customs people sure didn't care.