Here's a sample that introduces the gist of his argument:
This is history as big picture, detached and challenging. We moderns instinctively assume that everything about our circumstances is novel. Darwin repeatedly reminds us how a global view can emphasize continuity as well as change.
Yet because North America was from its white settler beginnings integrated into world commerce and industry, its cross-continental expansion launched the world's greatest economic power long before we got into the empire business ourself.
What Darwin believes requires more explanation that it usually gets is why the United States didn't get into the world empire business sooner, not really until after 1945.
Darwin's big picture, published in 2007, certainly adds dimension to our view of contemporary empires, especially our own. All those recalcitrant parts of the world that challenge the US imperium turn out to have their own history of enduring empire. I guess that shouldn't be a surprise, but I imagine that ancient Romans had a hard time realizing that Parthians and Iberians had their own histories also. The view from the top of the heap can be distorting. This is a useful corrective.