If it's an analogue world, then isn't it entirely possible that the land masses are different from ours and trying to place the world is simply over-thinking things? I've given up trying to place the setting historically – technology, clothing, buildings, etc. are all a mishmash of very different eras that makes little logical sense. tbh I don't think there is an answer to where and when, only what makes more or less sense and what Isayama thought was cool and wanted to include/needed for plot or streamlining reasons.