The largest ships of the US Navy may pail in size in comparison to other nations, especially when using the National Special Rules (being unable to field any large or extra-large vessels). However, their frigates were exceptionally reinforced with many guns. To represent this, US fleets gain discounts to both the Over Gunned and Sturdy upgrades. They are both able to better weather punishment whilst dealing out a substantial portion themselves.
Additionally, in a similar vein to British crews, US crews were routinely drilled and always receive the +1 bonus to hit rolls. This makes US frigates, the core of your fleet exceptionally dependable, though remember if you do purchase both upgrades on all your ships (even at a discount), you may find yourself outnumbered.
US Navy Fleet