Could Kaiser Germany have conquered the world?

[Aenlic]

Napoleon's was largely a European + Mediterranean. I don't think there has ever been a true world war, to be honest. Even WWII didn't include South America, at least not that I know of.

Umeu: The Mongols didn't conquer Asia, at least not the whole of it. No single state has ever controlled a whole continent, apart from Britain controlling Australasia, and perhaps anyone who first claimed the barren wasteland of Antarctica.

Actually, it did include South America; although all of the actions were naval or espionage in nature.

Brazil was an ally of the U.S. at the beginning of the war. Brazil was a major source of supplies for Britain and France during the early years of the war. After the attack on Pearl Harbor, when the U.S. declared war on Japan, Brazil had a problem. They had a very large number of Japanese immigrants living there (as was also the case in Peru, Chile and other countries in the area). They resisted declaring war on Japan in concert with the U.S. at the time. But they agreed to declare war on Italy and Germany following the U.S. response to Germany's declaration of war. I believe Brazil even sent some troops to fight in the Italian campaign on the side of the Allies.

The large Japanese population turned out to be quite a problem for Brazil. Some of the immigrant groups had been infiltrated by the right wing militarist Japanese secret society called the Black Dragon. There were various acts of sabotage at Brazilian ports, and German U-boats had an uncanny knack (probably the result of shared intelligence between Japan and Germany) for finding Brazilian merchant ships ferrying supplies to the UK. There were quite a few Brazilian ships sunk by U-boats in the Atlantic.

So, except for Antarctica (and there is some controversy regarding reports of possible Nazi bases built in Queen Maud Land in the Antarctic too!) every continent either had direct military action in WWII or sent troops.