Maybe others have commented on the lines and waiting times at the Lisbon airport, but ...

If you're taking a flight back to the US, get to the airport early, probably three hours before your flight. I can tell you there were a lot of panicked people in line with us who didn't arrive early and feared missing their flights.

When we were there, the lines for the automated passport check extended well into the food court at Terminal 1. A large number of the machines were shut down. Then the security lines are similarly long, as there appears to be an insufficient number of walk-through detectors to handle the crowds. We didn't use Terminal 2, which is mostly for the low-cost airlines that fly within Europe, but we were told it's worse there.

My guess is that Lisbon has become quite popular and that the airport hasn't caught up with the crowds.

Agree with you on this. When we were there several years ago, the issues of getting into the airport to return our rental car required patience as not enough people on hand to direct traffic to where you needed to go. At the time all the traffic seemed to enter in one lane whether dropping people off, taxi, rental car return, etc. We dropped off rental car and then took airport bus into Lisbon for the next several days. When we departed several days later, the signage was confusing as to where you needed to go and with international flights to the US, it is always advisable to allow adequate time, 3 hours would be the norm.