Land costs are not a big issue, especially when looking at the world as a whole. In much of the US, for example, the cost of putting solar equipment on some land is nearly two orders of magnitude higher than the cost of the land itself. If a country is land constrained, then in an era of cheap solar they'll lose heavy industry to other countries with more land.

If land cost ever did become significant globally for renewables then renewables will have already slaughtered the competition, by being cheaper by a huge factor.

Relying on another country for your energy needs isn't a great idea. We've long sought to be energy dependent. Doing so has led to less wars and less influence from outside governments. Are you really going to base your entire economy and civilian well being (because let's be real, we live in an electric world) on the promise that another country will always sell that energy to you at a fair price? Always? Never decide to change?

It's not relying on the other country, it's having your industry become uncompetitive and die. It's not something you'd have a choice about.

Land costs are indeed an immense issue. The exact figure of how much land needs to be covered in solar panels varies depending on inclination with the sun and weather.Its not too bad for countries like Australia that have reliable sunlight and plenty of land. But much of the energy consumption occurs closer to the poles, and with more frequent obscuration of the sun from weather. And these countries are typically much more population dense. Dedicating several percentages of the landmass of a dense country is indeed a substantial cost. And this isn't even getting into the require immense amounts of energy storage. We have 5 minutes worth of hydroelectric storage relative to our average 11.5 TWh daily electricity consumption. But hydroelectric is geographically dependent and hard to scale. We only have 10 seconds worth of battery storage, about 1 Gigawatt hour.

It's incorrect to say that countries never go all in on one energy source. Norway generates almost all of it's electricity from hydroelectricity. Iceland generates the overwhelming majority from geothermal. And France generates the lion's share of it's electricity from nuclear power. The last of these three is geographically independent.

Sure, Norway and Iceland probably don't have to build a single nuclear plant. Nor would some states like Vermont and Washington that have extensive hydroelectric generation. But other geographies can only make do with fossil fuels. Intermittent sources can mitigate this, but we'll always need a solution to fill in the duck curve until we either make a breakthrough in energy storage or some other carbon free form of energy. But we already have another form of carbon free energy, and one that is already working for other countries.

Can confirm that Germany is totally covered by solar panels by now.

https://www.independent.co.uk/news/world/europe/germany-gree...

https://www.cleanenergywire.org/news/german-renewables-recor...

https://www.pv-magazine.com/2020/10/29/solar-other-renewable...

https://www.ise.fraunhofer.de/en/press-media/press-releases/...

Germany also produces under 10% of its electricity (and an even smaller fraction of its total energy consumption) from solar power.