Are we sure this doesn't vary by country in Europe? In Spain and the parts of France I visited, a US full size was pretty standard for two people. Certainly none of the people I knew had rooms that would accommodate a king size
I have to stand corrected about the length. The sheet size I buy is 220 long but apparantly my bed is only 200 :) I just measured. It's 160 x 200 and no one would consider that a big bed. Our previous bed was much taller but now I'm not sure what size. Ikea says their most sold size is 180 x 200, and if you buy Ikea you probably have a small budget and a small house.
I'm sure it does vary country by country, I'm sure beds are longer in western and northern Europe since we are on average taller than southern Europeans. And yes, the smallest bedrooms/ homes I have personally encountered have been in the UK. But even in the UK I have never encountered a bed only 185 cm long. And I've slept in many private homes in the UK, not just in hotels.
A US full size according to google is 54" x 74" - 137 cm x 187 cm and that just seems really, really tiny to me. I have never personally encountered a bed shorter than 200 cm although I'm sure they used to exist at some point in history. I would say 200 cm (79") is a short bed and 220 cm (87") is a long bed. Beds 140cm wide do certainly exist here, we would consider it a "1,5". Fine for a single person who occasionally shares their bed with someone, or a student. Unless you lived in a studio apartment or something you wouldn't buy that size of bed if you were a couple sharing a bed every night.
I'm sure in some parts of Europe homes are smaller than in other parts, but I feel like I probably already live in a place with smaller homes/rooms than average. How much space does one need in a bedroom? Maybe 50 cm on three sides of the bed and the headboard to the wall? I feel that in many countries in Europe, at least in the homes I've been in, that would not be an unusually large size for the master bedroom. My own bedroom as I said is 11m2 and even though we have a 160 cm wide bed now, the bigger bed fit in comfortably.
I suppose if you're looking at the Hollywood film bedroom interior where there's a desk and a table and a carpet and a couple of chests of drawers, no, a bigger bed and all that furniture wouldn't fit in a typical European bedroom. Most people just have a bed, maybe two small sidetables. But I've always assumed that regular Americans don't have those type of ballrooms for bedrooms either.