You might as well argue that it's impossible to distribute beer to a country of 320M people, yet inhabitants of large countries don't go thirsty.

Whether we talk about a union of 320M as the US or a union of 510M as the EU, or whether we talk about a state like Michigan with 9M inhabitants or a nation like Sweden with 10M hardly matters. There are roads, electrical grids and similar infrastructure everywhere in the modern world.

It's not the distribution that's the problem. It's political will.

If anything this favors U.S.. In a small country, it is harder to balance out renewable energy sources, i.e. if there is no wind in Tennessee there is likely some in Iowa, but that doesn't work as easily for regions of Poland. And yet, they are doing it.

Most EU countries are connected to the grids of other countries to some extent (even the UK and Ireland have underwater interconnectors, though they're rather limited).

Energy distribution, be it from solar/wind/water/natural gas, is a question of logistics.