At its founding and for almost 200 years thereafter Americans identified men and woman as the two sexes. From Daniel Websters 1878 American Dictionary, the dictionary used by the founders and by generations after them:
Sex:
1. The distinction between male and female; or the property or character by which an animal is male or female. The male sex is usually characterized by muscular strength, boldness and firmness. The female sex is characterized by softness, sensibility and modesty.
Gender:
In grammar, a difference in words to express distinction of sex; usually a difference of termination in nouns, adjectives and participles, to express the distinction of male and female. But although this was the original design of different terminations, yet in the progress of language, other words having no relation to one sex or the other, came to have genders assigned them by custom. Words expressing males are said to be of the masculine gender; those expressing females, of the feminine gender; and in some languages, words expressing things having no sex, are of the neuter or neither gender.
Gender is what we’ve become because it facilitates the fallacious notion of nonbinary, transgender, homosexual, and so on. And because we've been deliberately dumbed-down, a majority of confused Americans use the word sex for what we do physically and fuzzy gender for what we are.
Thank you. Somewhere, I saved 2 old dictionaries - one being a D. Webster.
I wish I had not thrown out the old Britannica printed just after WW-II.