Question

What might be the short run impact of a completely open immigration policy that allowed labor to move freely across the U.S. border

Answer 1

it will be harder to stop drugs and illegal weapons from coming into the US due to the fact that there would be no checks and if there was it would be easier to scope out the people with and without identification

Answer 2

Increased US inhabitants,, extremely higher demand for jobs, maybe even shortages of them. Things like that.