The unmarried American males.

American women don’t want a man who is less educated, makes less money, shorter, or fatter, so an increasing fraction will remain unmarried and childless.

Plus more six feet, six figures, and six something else.

American men will increasingly travel to countries that have more women who want to be married than men.

By my calculations there are 60.3 million unmarried men between age 20 and 70 in the USA.

There are 312 million unmarried women between age 20 and 50 in Europe, Asia and Latin America, so there over 5 unmarried women for every passport bro even if every unmarried American man age 20-70 becomes a passport bro.

Every unmarried American man has something valuable to offer to a prospective bride: USA citizenship and access to the only major economy that is not going to crash in the foreseeable future.