A lot depends on the time if day and other arrivals. IAH is normally reasonable quick, unless you arrive at the same time as the LH A380. That day immigration took an hour.

Getting through immigration at IAD is normally pretty quick, but getting back through security can be a nightmare. Then, if your connection goes off the high D gate numbers, you have a 1km walk.

ORD is easy, if you have only carry on luggage. The one stop speeds things up. I have done "doors open" on an arrival to getting to B terminal gates in 30 minutes before now.

EWR. Don't go there.

SFO, relatively painless every time I've gone through there, and along with IAH, probably my favorite entry point.

LAX, can again be a pain because of the very small immigration hall. Two flighrs arriving similtaneously and you coukd be queuing out the door.