Don't rule out US anti-terrorism measures interfering with the shipment.

I sent a lens to a US buyer just after some scares with cargo planes carrying want-to-be bombs. This lens was as it turned out later literally shipped to the US. It spent a long time in between parties and didn't arrive until after a month.

Not saying this is the case with your shipment, but IME these US anti-terrorism measures are not always communicated well (for good reason perhaps) and therefore may interfere without you and others knowing.