Have a stock of the Transformers on hand. It takes a very long time to build and supply the critical transformers. Not the little dudes on the pole outside your house.
More than that, a lot more!
I believe you may be confusing the effects of a nuclear-explosion's EMP with the effects of a "Carrington" (solar flare) event.
A Carrington event would knock out the power grid, but would not destroy run-of-the-mill electronics. So it could be mitigated by:
1. A big stock of high-voltage transformers, per your suggestion; and
2. A warning system that would take the power grid's functioning transformers off-line temporarily when an incoming flare is detected.
But a nuclear EMP not only would cripple our power grid, but it also could fry most solid-state electronic devices (e.g., in all modern cars) under its "umbrella" -- unless those devices had been suitably shielded, grounded and otherwise hardened.
“Have a stock of the Transformers on hand.”
Good point... Even with the lack of probability of an EMP weapon being deployed, there is always the possibility of a solar flare or even lightning.
I would expect that the power industry already has some degree of redundancy built in. This is something that I would expect would be handled by private industry and not some wasteful government program.