European nations were created by the movement of masses of people, military conquest, and a slow process of cultural assimilation. As a result, the contract theory of government makes little historical sense there. William the Conqueror never made a deal with his new Anglo-Saxon subjects.
But America was different. The native population was pushed away and wiped out, not conquered and exploited. The newcomers, with the glaring exception of the slaves, were there by choice. They created an ethnic, cultural, and religious mix that was conspicuously different than the mother country, which was too far away, given the technology of the day, to effectively rule them on a day-to-day basis.
The new nation-state was consequently created by a successful rebellion and the subsequent consent of the population. Jefferson’s language in the Declaration is far from universally true, but it works for us.