RE: McMaster-Carr export issue.
If it goes USPS... and the value of the box is less than $2500... it can be exempt.
From the USPS site:
If the value of your shipment is less than $2,500, enter "NOEEI 30.37(a).
Unless you are trying to ship oil or other Hazmat items... I would think that's a catch all for most orders.