In Sweden we eat ketchup with a lot of things. Sausage, pasta (weird, I know... I don't like it myself), spaghetti, fries, burgers etc. The list goes on. Some people in Eastern European countries even put ketchup on pizza. It's not very common in Sweden though
I eat it too, but only with fries , I know some people eat it with pasta and pizza and I'm like whuuut... When my Mom first tried it as a teenager in the 80's when she was visiting Germany she was disgusted about the taste at first but then she was like meh :)
I like ketchup, I eat it to a lot of things, but I do personally prefer Italian tomato sauce muuuch better, especially when I add pesto to my food, ketchup doesn't go AS well as Italian tomato sauce does.
A lot of people love it on their sausage, with fries or even with cheese on a sandwich, but we're not obsessed with it. I personally don't really like it because the taste is too strong for me. It takes away the taste of the original food, so something a few drops on my sausage is nice.