Since all the us wine sold in canada is a tiny fraction of the dip in sales it literally can't have any real consequence. But enjoy your little theory.
> "In 2025 the U.S. wine exports plummeted 33.5 percent compared to 2024, driven largely by a 76.8 percent drop to its largest market, Canada, according to new data just released by the U.S. Census Bureau. In total, American wine exports fell from $1.3 billion in 2024 to $850 million this past year, a $428 million loss." [1]
So the largest export market dropped by 3/4 which led the total exports to fall by 1/3. I don't know how that is anything but a "real consequence"?
[1] https://robbreport.com/food-drink/wine/us-wine-exports-fell-...
Lets use your numbers then.
Total US domestic sales were about 3.3 billion liters.
Exports were about 253 million liters.
Exports, if they went to 0, would explain less than 8% reduction in wine sales.
But the article quotes a 20% drop.
Exports have decreased maybe 1/3 and that is only in the last 2 years, and that is by your own numbers. That would constitute a 1.5% drop, not a 20% drop.
So changes in exports do not have a significant effect on the numbers, and cannot explain a 20% drop, or even a significant portion of a 20% drop.