Question

What phrase was used to describe the the god-given right many americans believed was theirs with regard to expanding across the country

Answer 1

Unalienable rights Because in the preamble of the Declaration of Independence states, “... that all Men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the Pursuit of Happiness.”
Ps. I only copied the quote