1914 House rule for USW
The German player can roll for USW and still avoid war. However, each time they perform USW a D6 is rolled. It it hits 5+, the next score of the die is reduced to 4+ and finally 3+. When it hits 3, the US player is at war. Obviously, you don’t roll this is the US is already at war.
Now the German player can take chances and still avoid war and the CP have some small advantage.
Another system is to allow the US player while neutral to ship IPC on her Built transports. US can ship up to 10 IPC to UK as aid ( the US player now has less income to buy). The German player can target this income by sinking US transports. The income shipped is kept secret and written on a piece of paper under the transport. Each time the transport is sunk, the German player rolls a die like the system above, except the first score is 4+ not 5+. IN this really the German player has only one known turn that they can trigger war closer but not cause a war. Obviously, the next score is 3+, which most likely will cause war.
However, the note triggered the war anyway so who cares.
Would Germany have much chance of sinking them with the Atlantic just a couple of SZs wide?
Give subs a first-strike capability and you may be talking, but this will not make USW worthwhile.