Afaik the US barely exports to europe (especially your example sounded odd to me, i never saw american food on the shelf except cookies). I dont think it will affect the US a lot.
https://en.wikipedia.org/wiki/List_of_the_largest_trading_pa...
The EU is the largest trade partner of the US.
And when ordered by US Exports, the EU is the 2nd largest trade partner after Canada.
I suspect the problem you saw was related to American Brands (for food) vs the actual company behind the food. Many foods are bottled/packaged in local plants, and/or resold under local brands.
(Total US->UK ~$55bn, about 4% of total US exports, top categories: aircraft, oil, cars, machinery, electronics.)