Will Oremus at Slate makes fun of a Fox News subject-matter expert that thinks Germany gets much more sunshine than the US, and that's why Germany's solar power installations have proceeded more quickly than in the US. That position is absurd on its face; the Slate piece includes a nice graphic, courtesy of the US National Renewable Energy Laboratory (NREL), showing the solar resources available for Germany, Spain, and the US. Essentially everywhere in the US has more sunshine than Germany. Only Alaska is comparably bad. You have to wonder where this expert lives. Denver is not the sunniest place in the country, but even so, conventional wisdom here is that "if the sun doesn't shine for three days in a row, the whole city is ready to commit suicide." In Germany... well, this page with weather statistics for Bremen, in northwestern Germany, indicates a median annual cloud cover of 85%.
When the time comes that the US East Coast (and BosWash in particular) decides that it needs solar power on a large scale , there are two options. They can do local installation, which has some drawbacks: it will take more panels to generate a given amount of electricity per year than it would take in the Southwest ; there are significant periods when the sky stays overcast; much of the non-agriculture open space is wooded; and almost all the land is in private hands. The alternative is to build installations in the Southwest, along with high-voltage DC transmission lines to move the power east. In the SW, the sun shines more often, the sun shines more brightly, lots of the desirable areas don't grow trees, and there are enormous areas that are owned by the federal government. Any split that puts three-quarters of the US population on the side of "let's use a portion of those western public land holdings to generate power for us" gives them the votes in Congress to make it be so.
Is it reasonable to think that the East will want access to western renewable resources? Absolutely. NREL's Renewable Electricity Futures Study is one of the largest and most detailed studies available of scenarios under which the US achieves high penetrations of renewable generation. The fundamental model used in that study is a linear optimization that minimizes total costs. In the unconstrained scenarios, the amount of additional transmission capacity increases exponentially with increasing penetration of renewable power (see Figure ES-8 in the Executive Summary). The study identifies the principle use of that increased capacity as providing eastern load centers with access to high-quality western renewable resources. That is, western renewables plus long transmission lines cost less than eastern renewables. People may not always go for the lowest-cost option, but that's the way to bet.
And finally, is it reasonable to think that developers will prefer to make use of public, rather than private or state, lands? Again, the answer is yes, if that's where the resources are. Wyoming is by far the largest coal producer among the 50 US states; over 80% of all coal mined in Wyoming is produced from federally-owned lands (and much of that Wyoming coal is burned in states as far away as Georgia). Advocates for developing the Green River oil shale deposits in Colorado, Wyoming and Utah — a terrible idea, by the way, but that's a topic for a different day — are constantly pushing to open federal land, even though large high-quality deposits on private holdings are readily available.
Will there be an eastern grab for western renewable resources? I say yes, although it probably won't happen for 25-30 years. Will the western states resent it? Also yes. "Interesting" things may happen.
 For various reasons, I believe that time will eventually come. Reasonable people can disagree.
 Here "panel" means a photovoltaic panel, which can operate under a wide range of sky conditions. The advantage of locations in the Southwest is much greater for concentrating solar power, which requires direct sunshine.