>>2017401in NZ most people would consider a mixte or mixte-esque to be a woman's bike.
they were pretty much always marketed to women, and usually did not come in XL sizes, like women.
the logic was that you can modestly stand over the top tube in a dress
there is a valid physiological difference which is that 'women' tend to have longer legs and shorter torsos so 'womens' bikes have less reach.
Of course most bikes did not actually achieve this, it's achievable with fit adjustment anyway, and 'womens' bikes typically copied spec and were massively overgeared. And also of course, mixtes can be ridden by anyone and gender is a social construct.
full step through bikes were more unisex in terms of sizes and marketing. Mixtes were usually variants of the entry level sport tourers or road bikes, whereas your full step through is a sort of cruiser. Probably you are thinking of those.
Get over your obsession with America, mixtes being for women was pretty universal.