Maybe so, but anyway the speculation is fun.
Anyone, far more versed in this era and military knowledge, have any suggestions for the values of the several neutrals?
Considering that Spain had just been devastated by the Spanish Civil War, and was in no shape to do anything, a Zero IPC rating is probably appropriate, along with an immediate outbreak of a second Spanish Civil War. A repeat of what happened when the French tried to take over Spain in 1808 seems likely. All out, no quarter guerilla war, with the British happily supplying anyone who is fighting the Germans, which actually was likely to be everyone. Then, of course, you have this minor matter of feeding everyone. The US was shipping 700,000 tons of grain a year to Spain, simply to feed the populace. Germany could not match that. Hungry people tend to be very nasty. Probably the best thing for this would be continually put two infantry in Spain every turn someone is occupying it, and force them to continually keeping fighting to keep it in control.
If Portugal is attacked, then both the UK and the US had contingency plans to immediately occupy the Azores, which would have been of enormous help in combating the U-boat attacks in the Mid-Atlantic. Overall, the net gain would be for the Allies, big time. And at best, 1 IPC to the occupier. Angola and Mozambique would be the real prizes.
With respect to Turkey, the British were in staff discussions even before the war with the Turks, and were supplying them with military equipment as much as possible. When the US entered the war, the US started supplying equipment as well. The Turks had backed the Germans in WW1 to their great loss, and were not really interested in getting used again. Probably figure 4 infantry, an artillery, probably one fighter, and a naval ship, with the infantry defending at 3. Require a transport to get troops across the Straits, so for any attack at good odds, you are going to need more than one transport.
Switzerland, forget it. No one is going to attack Switzerland. If for some really bizarre reason, someone wanted to, figure 10 infantry in Switzerland, and the attacking force cannot use aircraft, artillery, or armor to attack with. And since the Swiss will be thoroughly dug in, they defend at 3. Enjoy.
As for Sweden, why? Again, it has to be an amphibious attack. Do not think about attacking from Norway over the mountains. They had a good army, navy, and air force, and you are not going to pull off the surprise like in Norway. Give them 3 infantry, 2 artillery, 1 armor, a fighter, a bomber, a cruiser, and some form of pre-emptive fire against any amphibious attempt.