For these reasons there is no PE:

4. Notwithstanding the preceding provisions of this Article, the term “permanent establishment” shall be deemed not to include: a) the use of facilities solely for the purpose of storage, display or delivery of goods or merchandise belonging to the enterprise; b) the maintenance of a stock of goods or merchandise belonging to the enterprise solely for the purpose of storage, display or delivery; c) the maintenance of a stock of goods or merchandise belonging to the enterprise solely for the purpose of processing by another enterprise;

The 3rd party he uses in the U.S. is simply to store and deliver goods. He has no control over that enterprise nor is it part of his company.