The NHPA is afraid of scaring off Canadians and anyone else from any other country that might come to the US to worlds to pitch.
The saving grace to the rule is that the shoe must meet the specifications. In other words this rule allows shoes that are in every way built legally, but the foreign manufacturer has not paid the NHPA sanctioning fee (since they don't sell horseshoes in the US).
I understand why they did it, but at it's core it is treating foreigners preferentially and it is treating US manufacturers un-preferentially. It is all the evidence anyone needs in order to understand that the NHPA is really, as the full association name indicates (National Horseshoe Pitchers Association of America), a wholly American organization, not an international organization. Were it so, the NHPA would have one set of rules that equally applied to all, no matter their country....at least they would for the "World" championships.
I've thought for some time that this leaves the door open to develop an "International" horseshoe pitching organization that could hold a true world championship. All they need is a set of rules and money, and the people will come...the more money, the more people. Such an organization could allow ANY pitcher, backyard - NHPA - Elks - German - Namibian - Japanese - etc, no membership or sanctioned tournaments required. You just register at the percentage you think you qualify for. A quick preliminary round will weed out the wanna-bes and set up a top championship bracket. You don't even need the money that the NHPA currently puts into the Worlds. Just top load it and the best will come and pay to come.
I'm a Legend...if only in my own mind...