Dana Zzyym, who is an intersex person, and the group Lambda Legal are trying to get an "x" gender. They argue that non-male and non-female people are forced to lie when completing forms for a passport, since they must either check the box "m" for men and "f" for women, which automatically does not correspond to what they are.
As we saw earlier, other countries already offer a third option on passports such as Nepal, Australia and New Zealand. Moreover, the passports of these three countries are recognized in the United States so there is no reason not to offer the third option to Americans.