oh well, i have just tried the strategy against an experienced player and i was destroyed terribly. SZ 12 IS NOT A SAFE PLACE R1. You would not have 2 UK trans in most cases. I played against bid 9 so there was one sub more from the start and an AC on G1. Any kind of convoying system is necessary for US but next time i am going to make sure that i control the atlantic solidly first. I made some childish mistakes too, but if the germans put an effort to contesting the atlantic you cannot just build trannies. You have to sink their ships first and you have to do it quick and as cheap as possible.
Btw if the convoying system is to work smoothly you need for US actually three sets of transport ships, two wount do.
Early allied shipping losses can really hamper your game plan. It is always vital to protect not only the transports, but that British battleship! If Germany invests 24 ipcs in the water, you will have to wait a round or two to be safe, however, thats all right, as Germany took away 24 ipcs from the Russian campaign, you have time to get going.