An EMP can be engineered to create more grid damage. But low frequencies require much more energy than high frequencies to induce currents. To get transformer-damaging currents with EMP would be quite difficult.
“low frequencies require much more energy than high frequencies to induce current”
I’m not sure you have a good understanding of what happens with an EMP. This is what happens:
1. The nuclear blast generates gamma rays that interact with the atmosphere creating an “RF pulse” that is intense and destroys many elements tonic systems
2. Scattered gammas and neutrons create a “lightning like” energy field
3. The expanding, then rising plasma ball surrounding the nuclear detonation causes geomagnetic field deformation inducing currents in the earth that can find their way onto transmission lines and into transformer windings. This is similar to what happens during a solar storm