In my opinion, the state of EHR interoperability should be attributed to the vendors of hospital information systems (i.e. Epic, Meditech, etc.) and their larger clients, big healthcare systems. Again, in my opinion, neither of these stakeholders has much, if any, incentive to develop and encourage a smooth or even mostly functional interoperability story. Every vendor wants to lock their customers into their product.
Software vendors see interoperability as a wedge into their lock-in on their customers, making it easier to migrate data from one system to another. I believe the incumbents fear an innovator rather than the other established players. But they would prefer to make it harder to migrate away from their systems, regardless of the target.
Healthcare companies want to keep customers inside the walled garden of their system and actively discourage them from moving to competing vendors. In their view, patients should receive all of their treatment from them or their close partner organizations. I don't believe that clinicians at these organizations are looking to hurt or bamboozle anyone; they are of the opinion that their healthcare organization provides a higher quality of healthcare. And, in all honesty it is safer: those partner organization who have access to the same central system will have access to all of the customer's data.
I once worked for a small healthcare system and my team designed and implemented software to transfer information from one organization to another through disparate systems. The organizations involved were partners, when interoperability with competitors was discussed this was quickly pushed aside: the project needed to be kept "cost effective" and these were "version 2.0" improvements. While these are reasonable arguments, communication with competing organizations was never implemented. The managers of the project were correct: it would cost money to implement this interoperability, money that would be out of pocket for the organization. And to what end? To help customers purchase a competing vendors products.
The HITECH act was meant to provide the money to fund interoperability. But now that I've worked for both healthcare and software vendors, it is less clear to me... What was the goal of the HITECH act? For the healthcare side, the goal was clearly to computerize the medical records and this was the cudgel used to force clinicians to carry laptops around as they spoke to patients; the organization I worked for managed to almost entirely eradicate clipboard usage. From the software vendor side the goals were similar, to provide the functionality required by the act in order to qualify as a "meaningfully useful" system. Interoperability between organization seemed to have been sketched in at the end and the guidelines didn't seem nearly as clear.
To my mind the question boils down to: how does the government (state or federal) incentivize interoperability? Clearly a single payer system would be the easiest answer: the government would be paying for all care and could simply demand this interoperability be present. While single payer isn't the only solution, I beliebe we will need a change of similar size to push these vendors into cooperating, despite the fact that it might hurt their bottom line.