Ironically, there are two nationwide networks for sharing patient data - CareEverywhere and Carequality. They even have a bridge between the two, so in effect it's one large network.
But that's all predicated on the provider's EHR being able to talk to it, or at least talk to an interface engine that can be configured to talk to it. And money. It costs money.
That's a different problem. The national networks have standardized APIs. Obviously the content returned will have some variations depending on the original source.
But that's all predicated on the provider's EHR being able to talk to it, or at least talk to an interface engine that can be configured to talk to it. And money. It costs money.