The belief that the u. s. was a "melting pot," which became very compelling in the first part of the twentieth century, suggested that the nation had an almost divine mission to produce

A melting pot, is a pot into which many different substances are going in, and then as they melt, they become fused with each other, - producing one substance. A melting pot as a metaphor means that the US was to produce a homogeneous society, a mix of all the constituent societies, which, it is to be understood, would be stronger than all the constituent societies by themselves. 

This act gave the federal government the power to relocate any native in the east to territory west of the mississippi river.