If I were the Germans, I'd take a more proactive role of unilaterally imposing a blockade on weapons and volunteers with my navy. Assert myself as Global Hegemon, help the Feds and make life more difficult for the Internationale. If they were neutral, I'd actually try and woo them into doing this, with promises of a free hand in Argentina and Chile. But things are as they are alas.
But active fighting would be better for 1. Keeping New England and her industrial capabilities away from Red Thievery. 2. Forcing them to actually fight a professional army who has spent the last decade or so preparing for an ultra hard war with officers who actually did fight in one of the biggest in human history. 3. Launching air raids on the Steel Belt immediately. These are all hard military objectives which we can immediately acheive in case of intervention. Yes, Paris and London may decide this means war, but i honestly don't think Berlin will. The Ententes goals of restoring their nations are not as of yet incompatible with Berlins. If things go south, they'll withdraw. That just leaves us facing the Internationale, and at the end of the day, they're across the ocean, and we're right here.
The sword suspended is often more useful than the actual execution.
If the Germans weren't sending soldiers to help Long, then they could drop by and casually mention that they're a neutral power, leaning Federal, and they would
really appreciate it if we didn't do anything to change that. Under those circumstances, I would not be in favor of Option #3.
Since they're already showing their desire to cripple and vassalize America, we have little reason to say
No to the Entente's offer.
Canada can help us in New England. They can send warships to begin blockading enemy ports immediately, with zero delay. They can help us with oil and shells and all the material of war, and they can do this before a single Canadian soldier enters battle.
Given their fear of the Internationale, I would be surprised if they don't have some soldiers and artillery in position near Detroit already. Even if they limit their attacks to artillery bombardments and coastal raids, the impact of an
active second front will be significant. Yes, the CSA would need to have troops there anyway, but now they'll be taking casualties and fighting on multiple fronts. We can expect significant damage to morale, as the looming threat on the northern border shows that any CSA triumphs in the east are built upon sand.
We could also have rifles and artillery from New England under Option #2 while those are protected by the Canada and oil is hardly in short supply in the US, if the CSA decides they want to have a go at it then splendid, Canada is dragged into the war without us needing to write that diplomatic check. I do not doubt that escalation may occur but I view it as the difference between actively inviting it and slowing it down.
Under Option #2, New England will have a tripline of Canadian forces that will either keep the Reds away entirely, or leading to Canada being dragged into the war without us having to write that diplomatic check. In World War 2, Canada was only able to sustain a single army on the field after thorough mobilization, no matter how well trained it simply isn't practical to for those forces to spell a quick end to the northern front, and I believe it would be rapidly outweighed by a massive increase in foreign volunteers. In terms of airpower, Canada's airforce is simply not capable of waging a meaningful strategic campaign against CSA targets, the Royal Air Force couldn't even really do it until 1942 at the earliest. Airpower as it stands at this juncture is predominantly psychological which can just as easily backfire, or tactical in its considerations. With Option #2 we could have the practical elements of still forcing the CSA to be wary of their northern border and the industrial advantages of New England, without having to dive headfirst into the escalatory spiral when we could just as easily make those commitments after the Civil War is complete.
I agree with most of this, which I why I approval voted for Option #2 as well as Option #3.
I think that neither the Internationale nor the Germans will rapidly mobilize a substantial number of soldiers in response to America siding with the Entente. But I could be wrong! I'm gambling about the actions of foreign powers. The Internationale's choices are shaped by ideology and wishful thinking, while the Germans are militarists with a dubious understanding of the Western Hemisphere, and they're led by a ruler who is notoriously fond of poor life choices. Option #2 is in many ways the safe option.
I don't imagine that Canada is a great military power. However, at the present time all of the factions are working with limited resources and a serious shortage of trained soldiers. None of us have full access to the industrial and military might of America, because we're in a civil war. Under these particular circumstances, Canada can punch well above their weight.
While I agree with your dismissal of the Canadian Air Force as a significant force, what about the Navy? Canada doesn't have our problems, and our enemies don't have much of a navy, so it seems that they could contribute a great deal by blockading Southern ports along the east coast.