I just made whole wheat spaghetti for dinner and the pasta is imported from Italy. We eat pasta imported from Italy all the time. So when you eat in the States, you may eat homegrown wheat, or you may eat imported wheat. It is not always readily apparent what wheat you are eating.

Does the United States import wheat as a raw product and not in the form of pasta?

Here is some info from Wheat in United States | The Observatory of Economic Complexity but I am not clear if this is just wheat as a commodity or including finished products:

United States imports Wheat primarily from:
Canada ($396M),
Poland ($2.14M),
Italy ($1.18M),
Mexico ($329k), and
United Kingdom ($211k).

The fastest growing import markets in Wheat for United States between 2020 and 2021 were Poland ($2.14M), Italy ($733k), and Mexico ($329k).

At any rate, it is clear that there is some Italian wheat in the US, albeit not as nearly as much as Canadian wheat.

Therefore, this claim that somebody got brain fog whenever he ate in the States would imply that occasionally that included eating wheat imported from Italy. Not every time, no, but occasionally. So that someone occasionally reacted with an allergy to Italian wheat consumed in the United States but never to native Italian wheat consumed in Italy? That claim sounds dubious. We do not have such a Chinese wall-like divide between the US and Italian markets.

And then the next claim is that because wheat in the US and Italy differ in whether they cause an allergy (in that particular individual), it may be concluded that wheat may or may not be linked to the development of Schizophrenia. I am not sure I follow the line of reasoning here.

And how is the data I provided supportive of this? My data showed the between India and China, the prevalence of schizophrenia is the same despite widely differing main staples of local cuisine. How does that data support the claim that consuming wheat may or may not be linked to the development of Schizophrenia? I am not clear how any data can be supportive of that claim because the claim is phrased in terms of "may or may not be linked". That claim is always true. So in a sense, yes, my data supports this claim but any data supports this claim because the claim is necessarily true. I am sorry but by now I am totally confused.