I wonder what the reason behind this restriction for USPS airmail to foreign countries might be:
f. The name of the sender and/or addressee may not be in initials except where they are an adopted trade name.
In addition, their own regulations and examples to not agree with each other:
k. The delivery address should be printed in all uppercase letters. The name of the place of destination and the name of the country of destination must be written in capital letters together with the correct post code number or delivery zone number, if any. If possible, the address should have no more than five lines. For example:
Mr Thomas Clark
117 Russell Drive
LONDON WIP 6HQ
ENGLAND
I’ll admit that I hadn’t realised that last. We’ll see how much of what I sent gets through.