The loss of the US convoys is not that terrible, together they are only worth ten (25% of US total income)
The game is not unbalanced if the allies are coordinated and work together.
Dear ANON long post (if you are still out thar),
What UK,US & SOV players would allow a GER AC to survive in the Baltic SZ after UK1, US1, or SOV2? This GER build would allow for a massive SOV INF overload that the German player could not beat.