I'm a big fan of Buchanan, always have been. He makes arguments that others are afraid to make.
But I think he's wrong here. It was said of Napoleon that he didn't want all of Europe, just those parts that bordered his empire. And as his empire expanded, so did the number of countries that bordered it.
Same goes with Hitler. He didn't want to attack the West...yet. If Britain and France would have stayed out of the Polish conflict, perhaps Hitler would have first driven east. Moscow then Paris instead of Paris then Moscow.
Hitler wanted revenge on the French as much as Lebensraum in the East.