Early, UK needs a couple transports, or he’s no threat to German income, and therefore ignorable…more Nazis to Moscow.
Those transports have to stay alive though, so UK usually has to be conservative and coordinate from round 2 onwards with the US.
US needs to build DDs early to help clear the Atlantic, figs and boms help too…if they don’t have to go to Russia, they can help clear the last of the subs, or the Med fleet if it’s wandering north.
Once the Allies have enough DDs, or the German threat is gone, US switches to nothing but loaded transports…maybe a fighter if he’s got money. UK can pretty much do as he likes, exploiting weaknesses and opening things up for the US.