The United Kingdom

England is one of the first countries that will battle with Germany and Italy, and I think is also one of the two most difficult country to play.

It first objective is to secure it's delivery of goods from other parts of the world. So in order to achieve this is to build a large sea fleet, with a lot of transports and a lot of escort boats. But when you build a large sea force it will be very difficult for England to defend its territory in Africa.
As England you just have to hold out untill Germany is at War with the USSR, or when the US joins.
When that happen Germany will get it much difficult and you can start building aan attacking force. Helping defending France will only cost you units and will not stop Germany long.

I advice to build some soldiers for Africa and for the rest only build the amount of transports you need for the holding boxes and for the rest only build escorts. Those escorts are needed to defend the transports and the holding boxes and they also keep the German invasion fleet at bay, and they must be used to attack the German U-boat threat.