I am currently visiting the USA, and before I leave I want to try some food that is "uniquely" american - IE, you can't really find it outside of the country.

UK stores do tend to have a "USA section" which has a small amount of sweets and other products. But I am wondering what americans specifically missed / couldn't find in other countries.

As an example - Wendy's as far as I've seen, isn't local to the UK or at least where I live. So trying that was a "unique american food", to me.

I'm also in Chicago at the moment, so I made sure to try a proper (real?) Chicago deep dish pizza (loved it, by the way).

Alternatively, any other suggestions of food to try?

Immediate edit - turns out Wendy's is in some locations in the UK. I just assumed incorrectly!

Thanks for all the suggestions!!