the declaration of independence declared that all men are equal so how can whites justify imposing the Jim Crow Laws across the south

The whites in the South tried justifying Jim Crow Laws by saying they were "separate but equal."

Explanation:

Jim Crow Laws were basically a way for the South to legalize segregation. Even after slavery became illegal across the United States, the South still tried to find ways to hold back African Americans.

Jim Crow Laws separated blacks and whites. They would have different bathrooms, water fountains, schools, pool tables, essentially everything. Southern whites refused to integrate African Americans into society and many still refused to see them as people.

They would say they were "separate but equal," even though they really weren't. Blacks were still treated very harshly and weren't given equal opportunities.

a system of cooperative federalism emerged, as the powers of the federal government expanded.

i would say it is the roman empire europe after the norman conquest.