Some of this reminds of arriving at Washington Dulles...
Got pulled over for a "random bag check", stood in a line for 1.5 hours (after already waiting an hour at immigration). 6 staff doing the random checks, but no more than 3 ever actually doing anything other than sit and talk to each other, the other 3 spent about 70% of their time just talking, and occasionally checking sometimes bag, hence a line full of people missing connecting flights.
Now, before all the replies...I know the US has to defend itself (obviously), the problem isn't that the security is done, the problem is the level of rudeness and general bad attitude employed by a not inconsiderable percentage of the first people you meet on arrival. Which is a shame, because the country is by and large very nice, not a good advert.