This is absolutely, 100% a big problem. While these FOIA’d FEMA docs [0] are just one source, searching for “solar flare blackout” will net you all the sources you need. It’s the same as a nuclear EMP.
[0] (PDF): http://www.governmentattic.org/24docs/UnpubFEMAgeomagRpts_20...
"NERC recognizes that other studies have indicated a severe GMD event would result in the failure of a large number of EHV transformers. The work of the GMD Task Force documented in this report does not support this result for reasons detailed in Chapter 5 (Power Transformers), and Chapter 8 (Power System Analysis). Instead, voltage instability is the far more likely result of a severe GMD storm, although older transformers of a certain design and transformers near the end of operation life could experience damage."
https://web.archive.org/web/20150908075507/https://www.frcc....
[0] (pdf): https://www.resilientsocieties.org/uploads/5/4/0/0/54008795/...
If you want a very in-depth review: https://doi.org/10.1002/2016SW001501
The long term damage from that is significantly less than assumed. Yes, making ultra efficient transformers designed to last decades is extremely time consuming, but building something less efficient in under a week is also possible. There would likely be various electrical issues until they where replaced, but that’s vastly better than societal collapse.
Consider, a modern ship’s propeller is an marvel of modern engineering that would be extremely difficult to replace with something nearly as good. But, welding some plates to the drive shaft is vastly better than nothing in an emergency. Similarly, if the choice is a poor solution or no electrical grid, having some power makes a huge difference.
The purple lines there stand for the highest voltage level of the grid which usually runs at 380.000 to 400.000 Volts(with a few higher exceptions). These and their transformers are the most vulnerable to what we are talking about.
What do you hope to 'McGuyvering' there with maybe 110.000 Volts when the whole structure and anything connected to that is designed, specified, and built for at least three times the voltage?
400kV is not directly stepped down to 33kV there are generally intermediaries at 132kV and or 66kV. So if you can send 132kV or even 66kV much of the equipment can be used.
Getting enough power to operate refrigeration and stop lights is a big deal. If you can only send 20% of normal power across those lines then that’s what you’re stuck with. In places such as Hawaii, local generation is close enough that your it’s no big deal, in others you may end up with rolling blackouts or charging 1+$/kWh.