I totally agree with the bottleneck problem in Jordan/Persia, in particular with larger valuable targets. But, with only a few pieces, but a long line of them, you would end up with a dead zone in Jordan/Persia. The US would/could have air support from Russian territory to help in this dead zone and the Japs tend to have most of their air tied up in Fortress Europe. If the US 8 or so IPCs ends up being an even trade for Jap IPCs and control over Africa is maintained, I say advantage allies.
I’m not sure if it is easier or that much easier for the allies to get forces to Africa, depends on the philosophy of the players and direction of the game.
I find that the allies tend to play on the edge, that the supply chain cannot be broken and flexibility often costs resources that are not are can not be invested. Ok, say the game has settled down to a typical rhythm, allied control of Africa, US fleet in Sz2, allied fleet shucking into/onto europe. At some point the allies make a choice that requires their supply chain of reinforcements to be steady, I find this occurs when they first land in the Karelia area and expect to live a round. At this point, does the allied fleet have enough strength/flexility/position to now start landing forces in Algeria? Even there, it takes them a few turns to move up to and take Egypt and move into the rest of Africa unless you move allied transports past Sz12 to Sz17/Sz23, in which case they are out of position to continue to shuck.
The Japs are attacked by the brits and start out with 1 transport typically, and typically build 3 on J1. A shuck between Sz36 to Sz60/61 develops dropping off 8 units per turn. An extra transport every round or two means all the output from Japan gets moved and slowly islands have units taken off to the mainland and attacks on Australia and New zealand with threats to Alaska and hawaii perhaps never pursued as lost opportunity of those units in asia is greater than the reward.
By round 5, and IC should be built on FIC and or India. I find it tempting to wander around with the Jap fleet but I avoid it with anything but the odd lone transport or sub. So, with a large Jap fleet in Sz34 BBs and CVs you can shuck infantry from India to Egypt that start out in Japan as builds but quickly move to FIC then India. Tanks that you build in the FIC and Ind ICs just drive there, clear Persia then as non combat moves drive them from India to Trans Jorden. Tanks there can hit Karelia or allied forces that move up to Lib, and Libya can be hit by the Japanese navy though it takes them out of play and subjects them to attack from Sz12. If the allies get too strong in Lib, pull back to East Africa and hammer them when they move into Egypt in force.
I’m not sure what the Germans would have to do if the Japs just used an idle fleet to hop from FIC to Egy, the capital ships are often under used, 4 transports must be reserved to offload from Japan and it would only take 2 transports to move meaningful amounts of infantry and artillery from India to Egypt with tanks just driving there. A large Jap force in Egypt is way more flexible than a large allied force in Algeria. Mind you, switching gears to Algeria means a jump in threat to Weu but only a 1 turn increase followed by a decrease once this is abandoned by the allies.