Denmark is larger than Maryland but smaller than West Virginia and not anywhere near the size of North Dakota.
Storing enough renewable energy to heat homes across the US northern tier isn't likely to happen any time soon, and not without considerable investment, then.
I'm at roughly 48 degrees N latitude, and solar cells do not get the incident angle needed to generate efficiently most of the year. Days are considerably shorter in winter than midsummer, too.
Wind is often too strong for windmills.
Temperatures in winter are commonly down to -30, and I have seen -60, not counting wind chill.
Renewables won't supply the needs for one state, much less the country, here in the US, and I'm not counting transportation. We are far more spread out than even the most sparsely populated European country, and even Agenda 21 won't change that.