Final answer:
Jefferson shaped the political system of the U.S. by advocating for democracy and authoring foundational documents, while Marx's theory of class struggle influenced revolutions and the establishment of socialist states, providing the theory underpinning social conflict theory.
Step-by-step explanation:
Thomas Jefferson and Karl Marx significantly impacted social and political change in their respective nations through their ideologies and written works. Jefferson, as a Founding Father and the third President of the United States, was instrumental in shaping the American political landscape by promoting democratic principles, authoring the Declaration of Independence, and expanding the country through the Louisiana Purchase. On the other hand, Karl Marx's contributions to socialism radically changed the socio-political structures in countries that adopted his ideas. His works, most notably with Friedrich Engels, such as 'The Communist Manifesto,' laid the foundation for Marxism and influenced the revolutions in Russia, leading to the establishment of the Soviet Union, and impacted other socialist movements worldwide.