"You have two cows" is a political analogy and form of early 20th century American political satire to describe various economic systems of government. The setup of a typical joke of this kind is the assumption that the listener lives within a given system and has two cows, a very relatable occupation across countries and national boundaries. The punch line is what happens to the listener and the cows in the system; it offers a brief and humorous take on the subject or locale.
A newer variant of the joke cycle compares different peoples and countries.