Sorry to come back on topic, but I wonder how the U.S. naval tech will work. If you take a historical approach, they shouldn't be able to build 1st and 2nd rates as these were rare in the US navy even in the 19th century. I think it would add "faction flavor" if you will, if they can only make frigates, and thus the only way to obtain a larger vessel of war would be to capture it (but not obtain the tech).