Well that’s really interesting Larynxa.
I always felt that how I visualize number sequences was to some extent connected to the math rods we used in first grades. Although this learned approach doesn’t correlate to my visualization of months and years. I can’t think of anything as a child that would have influenced it. I also visualize countries as part of map and usually with a label. But I since my father also has Synaesthesia I would sway in the direction of genetics being responsible.