Hinkley C is the first public nuclear power plant in the UK in decades. At current rate it will be 27 years between announcement and completion, at a cost of $30Bn USD equivalent, double the earlier cost and a decade later than planned. Brazil is building a 1GW solar farm [1]for a total cost of $750M USD equivalent. Algeria is aiming to build 15GW of solar in the next 15 years[2]; that's a country with a GDP of $150 Billion USD compared to USA's $21 Trillion.
+400GW of Solar in 50 years at Brazil's prices would be $20Bn/year. Solar has been dropping in price significantly in the past two decades and may do so in coming decades. Compared to +400GW of nuclear power at these prices, which would be $240Bn/year. Hinkley C has doubled in cost in a decade, and it's not certain it would be significantly cheaper if done again several times.
That's still not easily /doable/ for all the other reasons you've discussed about materials needed and power used in supply chains and manufacturing and limits of places to put it, etc., but it's a more plausible to commit a-COVID-response-per-year than an-entire-Apollo-Moon-landing-program-per-year for the next dozen presidential terms. The Elon Musk interview you linked, you say "We need to double power generation, it can't be done! It's impossible! Elon says so!" but Elon says "we need to double power production and distribution, which isn't going to work, that's why we make solar roof tiles, we need more local power generation, blah blah". He didn't seem to agree with you that it was impossible.
USA uses 21 million barrels of oil every day, Google tells me there is about 1.6MWh equivalent in a barrel of oil, or 33million MWh per day equivalent; over 24 hours makes about 1.3TW, approx the same as USA power generation. To replace all the oil use (in pure power terms not counting plastics, etc) with electricity would require doubling the power output of the country, yet a lot of the oil isn't used for transport, maybe half is used for transport. So replacing transport should be a chunk less than doubling power output. And it's not the case that transport needs to stay the same efficiency for the 50 years, e.g. how many of the 300M cars you talk about get less than 60mpg? Less than 40mpg? How many of them stop their engines at traffic stops? Elon commented that wing mirrors on Teslas cost up to 5% drag but can't replace them with cameras for regulatory reasons which could be changed. What if road speed limits were reduced to mandate more efficiency? What if delivery shopping was subsidised? What if work-from-home was given a tax break? What if double-car-ownership was taxed more? 50 years is enough to drive a lot of other changes in society if there was collective will.
I'm not handwavingly saying "it can be done easily", maybe it still can't; but I am saying that you are thrilling over the-sky-is-falling. It's not the case that the only possible variable is power production; power use can be incentivised to change.
The UK national grid is currently producing[3] 30GW, half of that from wind. There's 33M cars in the UK, if they all charged at the other commenter's suggested 750W, and needed charging every 5 days each, that would add 5GW of demand. The UK built 2.4GW of wind power in a single year in 2019. You're modelling 5x the population with 10x the cars and getting to 100x the power demand.
> "What do we need in order to accomplish the above? Cheap oil. What I mean by "cheap" is $20 oil, rather than $130 per barrel. Why? Because EVERYTHING we will have to make, move, install, manufacture requires oil. Everything. You can't build a power plant without a massive amount of fuel. The cables that move the electricity? You can't make them without oil. You can't install them without oil. Manufacturing parts, and structural materials (beams, etc.) out of steel and aluminum? You can't do it without oil. Plastics, electronic components, microprocessors, displays, computers, motors, car bodies, etc. Everything is based on industrial processes that depend on oil. Humanity cannot exist in its current form without oil."
I often think the only way out is through. We cant revert to pre-industrial life without billions dying and quality of life plummetting. Still, oil is finite even if you discount the CO2 burning. Making it 1/6th the cost would lead to increasing use; would you, and how would you, stop it being used for motor racing and plastic junk making, in 5x the quantity?
[1] https://renewablesnow.com/news/brazils-ibitu-energia-starts-...
[2] https://www.pv-tech.org/algeria-launches-tender-process-for-...