Hitler was not bent on world domination.
Like most people, I haven't read "Mein Kampf". But I understand it was his position that the Germans deserved the lebensraum that the slavs occupied. Since the slavs were subhuman, they could be exterminated or relegated to servant class. Hitler's ambition was limited to securing lebensraum for the German people.
Hitler hated the French because of WWI, but they were an inconvenience. He was really surprised to crush them so easily, but all that did was make it that much easier to turn to the East. He wanted a peace with the British in 1940; The Brits weren't buying. That much is pretty well known-- it doesn't square with Hitler having plans for worldwide dominion in 1940 at least.
You are --surely-- familiar with Hitler's order to his U-boats to avoid contact with U.S. ships. How does that square with plans for worldwide dominiation?
He was pretty annoyed with the Japs for attacking Pearl Harbor. His intuition told him to declare war on us. Ooops.
After he invaded Russia, he soon realized he had a full plate. If he ever considered world wide domination, it was between late 1940 and the fall of 1941 when he was stalled in front of Moscow.
Walt
There is significantly more to it than that, Walt.
Hitler desired the slavic regions, but he also desired other things. He sought the unification of Germanic peoples for example and sought this by expansion. He also desired, and sought with his ally Mussolini, a mediterranian conquest. The expansion possibilities beyond that were likely and are anyone's guess.
Evidence of the expansionism comes from a major plank of German national socialism's beliefs. Hitler and the Nazis believed themselves and Germany to be the embodiment of superiority in the world - in science, in technology, in ethnicity, in practically everything. The concept came out of the philosophical writings of German marxists during world war I. The nazis saw as almost a destiny the emergence and dominence of "Mitteleuropa" - the middle-lands of Europe, or the German states. They wrote on end about how the "Haendler," or merchants, were in a societal competition/clash with the "Helden," the heroes. Germany was to them, of course, the state of heroes in the world that was destined to win and owed the leadership of the world. It was a truly bizarre train of thought and one firmly rooted in marxist philosophy with a strong hegelian influence.