Most developed countries have their own comprehensive electricity grids, but it is common for neighbouring countries to have links between them so they can share resources and run their generating stations in the most efficient manner - which is at fairly constant load.
There are big power cables running under the sea between France and Britain, for example.
How strong those links are, must be unique to each; but the basic principle is that a failure in one area cannot or should not bring others down with it.
I don't the situation in the USA, but I would guess that many states cannot easily be self-sufficient in electricity, thanks to all or any of their geography, population, towns, climate and economy. I guess too you have wide variations across the continent in how electricity is used - California and Arizona might have all their air-conditioners running flat out when it's just a nice warm day in the North-Eastern coastal states. On the other hand the New Englanders need a lot more electricity for lighting and heating in Winter when the SW is more equable. And that's before the SE states get their power-lines felled by a hurricane or something. So you would need a robust national grid to help share the electricity around and cover for regional breakdowns. (A fully-integrated grid can sometimes bypass a broken transmission-line by providing alternative paths until the main one has been repaired.)
Lots of variables I guess. Well now our current worry is what to do about the attempted coup caused by the vile rhetoric of the dipstick duckhead. What happened at the Capitol will never be erased. His legacy. Attempted coup that failed. What will the insane weaponized adoring worshippers due next? I heard one say that they'd come back with more weapons. They wouldn't give up. They'd keep fighting. So I don't know what to expect next. Thank you for your thoughtful and informative reply Durdle! :)
I do really wonder what those intruders did intend. A coup? That suggests they would have taken over power, but then what? My feeling is that though they had wanted Trump to win the election and the rally and demonstration were to show that, most of them probably had no clear idea why they were invading the Capitol itself, or what it might achieve.
If Donald Trump had said, "Thank you fans! ", and brazenly stayed on as President on the strength of a coup, it could have been devastating for the USA's internal stability and international reputation, not because of Republican / Democrat politics but because he'd been put back there by a coup.
At least the Trump followers are not very likely to try to knock out the nation's power-supplies. How would they contact each other with no electricity to run the telecoms networks or re-charge their phones?
Many Republican voters supported Trump because they have grievances they thought he, or the Party, would address. If they do, those grievances need settling whoever is in power, but I think the rabble element is probably a tiny minority of them. They look many because they turn out on the streets in large, noisy and very intimidating flocks.
I reckon that despite that invasion and Trump's behaviour, your country's main problem at present is still the same as everywhere else - SARS_Covid-19.
"Intruders"? You mean the imbecilic insurrectionists who came equipped with weapons and nooses and twist ties who planned to HANG Mike Pence and Nancy Pelosi and take hostages? "INTRUDERS"? Massive understatement don'tcha think? Thank you for your reply Durdle. Of course I live it up close and personal. You are across the pond safe from TRAITOR DON and the imbecilic insurrectionists. They intruded 5 people who died. They planned to intrude many more. They still plan to intrude a lot more.
Durdle 