The problem is that Christianity just doesn't have room for the fey. Recently, there's been an outbreak of angels in popular culture, but they're not very interesting; they're all on the same side. (I gather the forms of Christianity that like the idea of guardian angels would rise up in arms against any story that took the logical step of including devils for the angels to fight.)
You'll have to look beyond Christianity. Some forms of New Age and Wicca seem to include a belief in pervasive spirits; but the problem there is that you won't be resonating with readers who don't hold those beliefs.
So, let's see. We can't find spirits in commonly held American beliefs. You don't want to import foreign spirits, because they feel tacked on. The standard American answer is to build our own; but, of course, that won't distinguish itself from a host of other fantasies that talk about the Tricksies and the Tracksies, or whatever.
Perhaps you could solve the problem by importing it into the story. A group of spiritualists are disappointed that America doesn't have its own spirits, so they set out to create their own. They might do so by magic (summon up raw spirit and shape it into a form that makes sense to Americans), or they might use technology. Personally, I think the tech approach works better; it fits into the "American ingenuity" meme/myth. The spirits might take the form of AIs which spread as viruses through the Internet—you can make them more effective by setting the story around 2020 or so, when you can postulate ubiquitous wireless broadband, cameras, and CPUs. You could have just a few spirits (Greed, Ingenuity, Hard Work, maybe more), each working as a distributed system; each CPU infected with a Greed virus is then running part of the Greed AI. Each camera that CPU can access is one of Greed's eyes; each machine it can control is one of Greed's hands. If the tech background includes augmented reality, then the spirits can really invade my sensorium. Ingenuity can look through my eyes and highlight the book in the library that includes a clue to solve the problem I'm working on; Hard Work can keep me from smelling the popcorn that might distract me from my problem; Greed can filter my hearing and amplify the conversation in the next cube about the new gadget it thinks I should want.
Angels
You'll have to look beyond Christianity. Some forms of New Age and Wicca seem to include a belief in pervasive spirits; but the problem there is that you won't be resonating with readers who don't hold those beliefs.
So, let's see. We can't find spirits in commonly held American beliefs. You don't want to import foreign spirits, because they feel tacked on. The standard American answer is to build our own; but, of course, that won't distinguish itself from a host of other fantasies that talk about the Tricksies and the Tracksies, or whatever.
Perhaps you could solve the problem by importing it into the story. A group of spiritualists are disappointed that America doesn't have its own spirits, so they set out to create their own. They might do so by magic (summon up raw spirit and shape it into a form that makes sense to Americans), or they might use technology. Personally, I think the tech approach works better; it fits into the "American ingenuity" meme/myth. The spirits might take the form of AIs which spread as viruses through the Internet—you can make them more effective by setting the story around 2020 or so, when you can postulate ubiquitous wireless broadband, cameras, and CPUs. You could have just a few spirits (Greed, Ingenuity, Hard Work, maybe more), each working as a distributed system; each CPU infected with a Greed virus is then running part of the Greed AI. Each camera that CPU can access is one of Greed's eyes; each machine it can control is one of Greed's hands. If the tech background includes augmented reality, then the spirits can really invade my sensorium. Ingenuity can look through my eyes and highlight the book in the library that includes a clue to solve the problem I'm working on; Hard Work can keep me from smelling the popcorn that might distract me from my problem; Greed can filter my hearing and amplify the conversation in the next cube about the new gadget it thinks I should want.
Could be pretty scary, actually.