Ordered 6/28 early morning. Registered myUPS about 20 minutes ago. JUST received an email confirmation telling me I registered. Clearly their servers are either slow or they are being hammered by all of us / xda right now.
I have noticed a good number of tracking information posted so far has delivery for 7/13 (tomorrow). Indianapolis was one of the locations.
Point being, I don't think these were ever sitting in warehouses in the United States. ASUS just shipped these overseas and Google is rerouting them. Something happened logistically causing the delay. Logistics for some of the retail units (like GameStop) were probably done differently, and thus not part of the problem.
AOSP 4.1.1 -> ASUS Updates -> ASUS Ships to US -> [something delays] -> Google Reroutes to Play Pre-Orderers
(this is what Apple does -- replace asus with foxconn)