I just finished a Global game, and the Axis took America by Turn 6. How? Germany did a Sealion feint, Italy took Gibraltar, and Japan took Hawaii on turn 1. Then, Germany moved their Sealion feint units into sz103 (from 112), Italy moved a lot of cruisers and destroyers through Gibraltar and took Brazil. Japan feinted into Alaska with 1 inf. The USA retook Alaska, built up the fleets in 101 and 10. Turn 3, Germany takes Newfoundland, Italy takes Central America, Japan takes Western Canada in force and destroys sz 10 fleet. Turn 5, Germany takes EUS, Italy takes CUS, and Japan takes WUS. UK Europe tries to take EUS with 4 turns of build-up in Quebec (and fails). Turn 6, Germany takes Quebec.
The Axis won by Turn 8. Germany lost Normandy and Holland to UK Europe, but held West Germany and Paris, and won by taking Leningrad. Italy, which had lost North Africa completely, managed to use its +15 IPCs to launch a force towards Cairo. Japan took Hong Kong and Manila.
The US player was fairly new, so this wouldn’t have worked otherwise.