A great debate shaping up here: VDH and Pat Buchannan
Buchanan responds here: http://www.townhall.com/columnists/PatrickJBuchanan/2008/06/13/the_good_war_and_the_terrible_peace?page=2
I haven't read Buchannan's book, however you can find his summary of the thesis here: http://www.townhall.com/columnists/PatrickJBuchanan/2008/05/27/how_the_west_lost_the_world
My take on the argument is, Buchanan has some interesting notions - but he's doing allohistory, Hanson is doing history.
Allohistory is the history of the "parallel universe" where X happened instead of Y.
Allohistory is a useful exercise sometimes and a lot of fun, but you cannot prove anything with it. Or rather, you can prove anything you like with it.