Please tell if you have first hand experience for this situation or post a source link. As far as I know they only allow people from certain countries to travel without Transit visa and Pakistan in not one of them. Us airports are different than Europe / ME because there is no corresponding international transit areas there. They don't allow Pakistanis, unless they have prior approval.Xmen said:Transit visa is required only for those who will stay more then 24 hrs during their transit station. Otherwise no need for TRV if you are catching up next flight within 24hrs.
More information here
http://travel.state.gov/content/visas/english/other/transit.html