What are some foods/clothes/souvenirs that are unique to USA?

I am going to an international conference, where we’re expected to wear attire that is representative of our country and also bring some food/drinks/souvenirs to share with people from other countries that is also unique to USA. I will be driving over 10 hours to this conference in the 80–90 degree weather so this fact is important in choosing food/drinks to carry. For drinks, alcohol is acceptable too.

Edit – But I could hold off to get them in the last few hours of driving that I’m in the country if they are found in practically any grocery store etc.

When I think of national clothing, I imagine something like cowboy boots/hat, or some native american attire? Unfortunately I don’t own any of these, so I am looking for a) more suggestions or b) how/where I can acquire this stuff for cheap.

Apparently people love Obama paraphernalia, but other than that, what souvenirs can I bring? And is there a place where I can find this stuff cheap to free? Thank you for any suggestions as always!