At the end of the 19th century and the early part of the 20th century, U.S. territorial expansion went way beyond what we now call the lower 48 states. Today we spend the hour with University of Chicago historian Bruce Cumings.   His 500-page tome, “Dominion from Sea to Sea: Pacific Ascendancy and American Power,” connects the history of our Western expansion with our Pacific history and the rise of American military supremacy.