The USA sends 3 resources to Japan and 1BP to China via this convoy route, so there should be enough capacity in the route.
Maybe I am missing something but I suspect a bug. Perhaps the program doesn't recognise the USA is allowed (per option 17) to use its own Concoys? Earlier in this game the USA was allowed to use its own convoys to transport the resource from Phillippines to China, so it looks like resources are handled the right way, just not the build point(s).






