This is just so untrue. There's tons of fast food restaurants all across Europe. There's a McDonalds in most historic city centers in Europe, and often a Burger King and a KFC as well. You picked Olive Garden as an example, and it's correct that they don't have any franchise locations in Europe, but there's plenty of American fast food (and fast casual to some extent) in Europe from other brands.
Look at this list: https://en.wikipedia.org/wiki/List_of_fast_food_restaurant_c...
The US section is significantly larger than any other country. Having lived in Paris, the French are missing out on a ton of amazing fast food options.
What they don't have is that sit down casual niche, of deeply mediocre and inexpensive food. It's filled with trattorias and bistros, which make the food in house. It's slower and pricier and smaller portions, but the food is made with more care and they feel that deeply.
https://www.npr.org/sections/thesalt/2013/07/08/200106073/fr...