The other NATO forces exist in the campaign, but they are abstracted in so far you do not directly interface with them. Whether you perform your mission orders or not influences the big picture: NATO CVBGs and convoys rely on you to successfully deal with potential threats against them. You do get position updates from reconaissance aircraft, SOSUS and satellites and if you ignore enemy forces, they will cause friendly casualities and impact the overall war. But other than mission-critical info, as far as command is concerned, you're on a need to know basis