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(Full disclosure: An ancestor was a Marine on the Ranger (1777), I do not believe that wiccan spells have any actual effect except psychological, but I understand that you might, and I want to hear from your perspective what the interaction would be.)
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I personally think they have about as much chance of moving the Marines as they do of moving Mt. Everest. And for rather similar reasons. There is, as you call it “esprit de corpse” is firm, long established and hardheaded as all get out. 
The following is The World According to Me, and steals ideas not only from Wicca but from Qabalah, Golden Dawn and my own personal meditations on Life, The Universe and Everything. Please don’t think anyone else specifically shares these ideas - many people do, but I’m not speaking for the group here.
The Marines are definitely a group with a powerful presence in the physical world, and you don’t get that way without a powerful presence in the (for lack of a better term) spiritual world. Everything that exists starts in the world of Formation before it can exist in the world of Creation. You have to have an idea about something before you can make it in physical form. When lots and lots of people share that idea, it becomes manifest more quickly and more strongly. Thousands and thousands of people over many years have fed this idea, that thought-form, to create the spirit of the Marines. This spirit is what allows the physical existence of the Marines to be as strong as it is. With enough mental, emotional, psychological and, perhaps psychic energy, this spirit, this thought-form, takes on a life of its own. The *idea *of The Marines has power, even when the physical Marines are not present. That’s an egregore.
It’s not just Marines who feed it. The media, video games, our personal impressions, thoughts and ideas about Marines and Marine life - those all feed the egregore, too. You could, theoretically, kill every single Marine and former Marine in the world tomorrow. But unless you destroy everyone who has a link with that egregore, you will not have destroyed The Marines. They would rebuild and return, created and sustained by that egregore.
IMHO, this is why long standing non-religious institutions like racism are still around. We haven’t destroyed the egregore that powers them. We’ve done so much on a societal level to try and eradicate people’s racist behavior, but we haven’t been able to stop the group thought form that empowers those behaviors.
It is a mystical spiritual thing? I have no idea. Is it the psychological bond of soldiers? Sure, absolutely. Is it societal inertia? Of course. Is it a philosophical construct best pondered late at night after a few intoxicants of your choice? Quite possibly. Quite probably, it’s some of all of the above.
I’m an agnostic myself. I’m not an atheist only because I can’t be sure there isn’t a Divine any more than I can be sure there is one. Yes, I’ve been the vessel for the Goddess to work through, more than once. But what does that mean? Does it mean I can get a certain part of my brain to light up more easily than others? Does it mean I’m delusional? Sure, could be. Could also be a literal Divine being sitting in my cerebrum telling me what to say for a while. I don’t actually think those are mutually exclusive, anyway. Maybe that “religious center” of the brain is where The Universe can plug in. Or it could be a flaw in the design of the neural network. I dunno. I think anyone who says they do know, for sure, is lying. The most any of us can do is suspect.
(Sophistry and Illusion, Roman Catholicism is widely recognized among neopagans as the most pagan of the Abrahamic religions. If they had allowed me to be a priest and had slightly different views on gay and reproductive rights, I would have been quite happy to be a part of their church. They have just beautiful rituals, not to mention the best sacred music ever written.)