No Twinkies in the UK! You probably don't have Moon Pies or Raspberry Zingers, either.
They are all 3 junk food that you're better off not eating anyway because they are full of preservatives. The Twinkie is a yellow cake with marshmallow creme in the middle. Sort of like a lady finger or eclair but with enough preservatives to keep it fresh for 5 years.
Our traditional foods to compare would depend on what part of the US you talk to. My favorites are Jambalaya, deep fried & spiced crawdads or alligator, gumbo, crawfish etouffee and basically anything else prepared by a cajun or creole cook! No, I'm not from Louisiana but I must spent several past lives there because it feels like home. Grits is definitely unusual but I think you all have something similar.
Around these parts, traditional is probably boring. Roast beef/turkey/chicken/pork. I guess barbecue might be something you all don't do much of over there but it's a regular thing here. Fried chicken. Chicken Fried Steak might be unusual. I'm curious to see what others pop in with.
My sister went on a 2 week tour of Europe about 15 years ago & was most surprised about the non-refrigerated and lack of ice in soda than anything. They mostly ate at American chain restaurants while on their tour, though. They were teenagers at the time so McDonald's & Hard Rock Cafes is where they ate.
I would be stopping in every little cafe along the roads asking for the special. Hubby & I love to try new foods.