are flight delays common in the US? ive been flying very regularly primarily around Asia for around a decade. (every 2 months or so) and ive never had a flight delayed more than hour (last minute at the gate always) anything longer.. i could only imagine it happening if there was a typhoon or something

Mechanical difficulties, weather esp. snow, air traffic control hold on incoming flights, etc. I wouldn't say >1 hr. delays were necessarily common but they're not rare either.

In my experience it depends on the route. I use SFO a lot and delays are quite common there because the they get a lot of fog and their runways are too close together for regulation to allow use of adjacent runways under bad visibility.