The political situation is different from normal axis and allies
From Axis and allies 1940 europe second edition rule book p.10
The United States may not declare war on any Axis
power unless an Axis power either declares war on it first
or captures London or any territory in North America,
after which it may declare war on any or all Axis powers
on its following turn.
The capture of London is not included in the notes of the tripleA engine, this can have a major impact on strategy if Germany wants to do sea lion.
@Simon-Håkansson Right, but the engine behaves as expected: When London is captured USA is enabled to declare war on Germany and Italy.
Generally, the notes of the games of the 3 Global maps are in need of overhaul, also since the engine issues are not completely correct and partially obsolete due to recent changes.