The tradeoff in an earlier US coastal blackout

What if the United States had imposed a coastal blackout earlier in the Second World War?

The result depends on navigation: darkness would hinder U-boats, but it could also endanger American ships without suitable aids and experienced crews.

Blackout conditions would make the American coast harder for German submarines to navigate. The same darkness would also complicate navigation for friendly merchant ships. Britain had a pool of navigators and captains with First World War blackout experience, including officers trained by that generation. American shipping lacked the same accumulated experience, so an earlier blackout cannot be evaluated separately from the aids and training available to its own crews.