You have to remember that the rail capacity in Africa, the Middle East, Asia, and South America is only one unit. Linking Egypt and South Africa would only cost 4 IPP so that’s not too bad considering you can only move one unit. Going from India to Egypt though would cost 10 IPP because of the terrain and one more link. That might be too steep a cost to only move 1 unit. It would cost 18 IPP to complete the link from the US to South America. If the rail capacity were unlimited then such links might be ok, but spending that much to move only 1 unit is probably not worth it. Especially a long link that can be damaged or broken by the enemy in an exposed place like the Middle East. I really like the idea of Cape Town to Cairo though.