black and white tiny screen TV's that (most) people seem to have is like, 40's or 50's right? the style of telephone seems to match that general era
but then the background people look like they're from the 80's (or Lilo & Stitch)
Kiki and her family (minus the pocket radio and her dad's car) seem to be living further in the past with no TV & phone (that's shown anyway)
and then there's the fucking dirigible
the country Kiki ends up residing in would probably be easiest to figure out if I actually took the time to write down any of the signs that are shown in town
although I think Europe has a lot of language overlap between country boundaries so maybe it wouldn't be easier
and then there's the tl;dr maybe it's just a mishmash of things that seem charming because it's a movie