I have not written about which foods one should taste in every European Country just the ones I have been to (and a few extra) and I have written about mostly foods that I have tried and liked and some that have been recommended to me.
In England: Fish and chips, High Tea!!! A full English breakfast, Sunday Roast, Bangers & Mash – some people complain that English food is too bland but just throw some malt vinegar and salt on it, trust me, it’s delicious
Scotland: Haggis (it tastes like a wet hamburger i swear), neeps and tatties, deep fried mars bar
Ireland: Full Irish Breakfast – similar to a full English, A Guinness, Champ, Irish Stew
In France: Macarons, Escargot, cheese, so much cheese, baguettes, crepes, steak tartare, bouillabaisse, duck, basically step out of your comfort zone in France and you will be pleasantly surprise, I am the most picky eater and I was surprised to find that Escargot is tasty!
In Germany: My favorite country for food and beer! Have a stein or five of beer, sometimes they mix it with lemonade (yum). Try schnitzel, bavarian pretzels, bratwurst, Kasespatzle, basically anything in Germany is delicious in my opinion.

In Spain: Tapas, Sangria, Paella, Churros
In Greece: Gyros, Lamb, Ouzo, Shish-kabob, Spanakopita, Tiropita, Feta cheese, Greek food is delicious but I am bias because I am Greek!
Turkey: Kebabs, Baklava, Mussels stuffed with rice
In Italy: Wine, Bruschetta, Venice has good meatballs, Rome has good Spaghetti and Pizza, depending on where you are in Italy certain parts are more well-known for different types of food, such as in Naples one of the most popular things to eat is deep fried pasta balls filled with pork. Have a shot of espresso or a cappuchino but only after you eat!
Belgium: Waffles, Mussels, Belgian Frites (YUM)
Netherlands: bitterballen, stroopwaffle, Dutch Fries, croquettes, drink plenty of Heineken, (personally I found Amsterdam to be the most disappointing city I have visited -food wise- poffertjes were my favorite thing I had besides the Dutch fries. I felt the food is more “snack food” but it is cool to get food from the “vending machines”. I am sure other parts of The Netherlands have better food than Amsterdam, however.
Poland: Peirogis, cabbage rolls, Polish pancakes, Roso, a broth/chicken soup, Herring
Sweden: Swedish meatballs with Lingoberries (interesting, bitter taste), Sweden had the best coffee I have ever tasted (and the strongest too!) Pancakes, Pie, open-faced sandwiches
Czech Republic: roast pork bread dumplings and cabbage, trdelnik, a type of cinnamon bread-rolled dessert, smažený sýr or a sort of deep fried cheese
Croatia: Stuffed peppers, mussels, fish stew, Fritula, beef stew, Buzara, Strukli, I found food in Croatia to be good and inexpensive
Hungary: Goulash, Langos, or deep fried flat bread, Porkoit, a sort of meat stew with dumplings, I have never been to Hungary (yet) but if I do visit I imagine this is the first dish I would love to try!