These kinds of arguments don't really add up if you use some system thinking and extrapolate from current trends.
First, the US isn't northern Europe (where solar energy is very popular regardless). Especially the southern half is more comparable to southern Europe or even North Africa. Places like Berlin are at 52 degrees latitude. You have to go deep into Canada to find cities at a similar latitude. Most of the US is below 49 degrees and gets decent amounts of sun. It's more than fine most of the year. If you regularly need to wear your sun glasses in January, you live in a place that can have solar power.
But sure, the Sun doesn't always shine and it gets grey and cloudy sometimes. Even in San Diego. But there are also wind, and batteries. And people always forget that you can use cables to move energy around as well. And a lot of cables aren't at their maximum capacities all of the time. So, they can be used to move energy around when it isn't needed and be used to charge batteries close to where it is needed later. San Diego is basically at the same latitude as places in Northern Africa that might end up supplying power via HVDC cables to Europe. The US can mix off shore wind on both coasts, solar across the south and its deserts with hydro in mountainous regions and lots of batteries. At this point very doable already and long term only getting more obvious to do as cost and efficiencies continue to improve.
Finally, modern batteries already last quite long. LFP and sodium ion are basically getting lifespans of 5000 or more cycles at this point. That's basically decades with normal usage and over a decade even with full daily cycling (which would be intensive usage).
Sodium ion means lots of dirt cheap batteries for storage and (small) vehicles. Basically it uses no rare materials and lasts a long time. It has the potential to decimate the cost of batteries from close to 100$/kwh to more like 10$/kwh by some estimates. At 10$/kwh, most house holds would be able to afford to have a mwh battery - enough to power an inefficient US household for a month. And a more efficient household throughout even the longest imaginable type of dunkelflaute. You can't quite get those yet of course but at this point we have some reason to be optimistic about this being possible mid to long term at least.
Add nuclear, hydro and geothermal to the mix and you have a lot of clean ways to generate and move around clean energy. That kind of system takes time to build but there really aren't a whole lot excuses not to.
This transition period has a lot of people looking in the rear view mirror being blind to the huge stuff that is clearly visible ahead at this point. There are a few wild cards that are interesting but not that essential. Like small reactors, fusion, etc. Nice but not really that essential.
The dunkelflaute is an interesting technical and infrastructure challenge that requires some out of the box thinking. But it's very solvable and it doesn't require any major new technology breakthroughs. We just need to do more of what we're already doing and preferably a bit cheaper. All very doable and within reach. And we have time to do it as our old infrastructure isn't magically about to disappear. Most of this stuff will be cost and economics driven.
Lots of countries that are ahead of the curve might be importing progressively less oil in the decades ahead. That means their trade balances shift and they start having economic growth and a competitive advantage.
IMHO countries that are lagging here will first fall behind, suffer the economic consequences for a while, and then fix it by compensating with massive investments. The US seems to be doing all the wrong things to set itself up for exactly that right now. Which is why I'm quite optimistic it will figure it out eventually.
