An extreme solar flare like something that happened in the 1870’s would affect the whole world. The damage would be extreme just like a man made EMP event only on a wider scale.
“For those of you that have been doing your reading, you already know that a nuclear EMP delivers three forms of energy. These are called; E-1, E-2 and E-3. E-1 and E-2 do not occur during a massive Solar Flare/CME strike on our planet. If you want to know more about E-1 and E-2, I recommend:”
The E-3 pulse will take down the power grid. “E1 is the component that can destroy computers and communications equipment; and it changes too fast for ordinary lightning protectors to provide effective protection against it.”
“According to the United States EMP Commission, the main potential problem with the E2 component is the fact that it immediately follows the E1 component, which may have damaged the devices that would normally protect against E2.”
“The E3 component has similarities to a geomagnetic storm caused by a very severe solar coronal mass ejection (CME).4, 5, 6 Like a geomagnetic storm, E3 can produce geomagnetically induced currents in long electrical conductors, which can then damage or destroy components such as power line transformers.”
It’s the E1 that will kiss your smart phone good bye.
The Carrington Event to which you are undoubtedly referring occurred in 1859.
We would, unlike in a nuclear EMP attack, have enough warning to shut down critical infrastructure and prevent many problems. People would have to do without electricity for a few days at most, and that would be bad but not catastrophic.
A wild card would be the nuclear reactors, both here and abroad - I don’t know if they can just be shut down, especially the cooling aspect. If not then we need hardened reserve generators in place at every nuke plant, with fuel for a minimum of a month. That, for every single plant worldwide, is orders of magnitude cheaper than a single meltdown anywhere.