From the BizJet side of the fence, the US CBP are relatively swift. I think the worst we had was sitting with the aircraft door closed for about 10 minutes in Teteboro while waiting for the all clear to disembark passengers (and their dog who was desperate for a pee!)
It is the Russians that seem to feel the need to go through your passport 2 or 3 times checking each page of your passport under the UV light.
Typically it takes a crew of 3 between 30 & 45 minutes to enter the country.