Also if Japan holds off until J2 to DoW, but the US player is either dead certain it will happen or hopes to discourage Sea Lion, they can slap a Naval Base on Greenland and load it up with their starting Atlantic forces US1, then drop the troops off in Scotland or Ireland US2. If London is saved at that point, you’re still in a decent position to threaten landings from France to Norway, or even farther if the UK player can be accommodating enough to give you a Naval Base.