I'm not sure I really believe Lucas on either assertion. It seems more likely that he wants to be known for having strong political beliefs and for creating art with a resonance beyond Taco Bell cups. Empire-as-America is the most convenient trope, though it's not really reflected on screen but for one ham-fisted "with us or against us" line in Episode III. Though the world really was enduring a hard grind during much of the prequel trilogy's run, the films themselves never escaped a certain plastic gloss. They were hardly an escape because they were essentially about a war, but the war depicted was so inauthentic that audiences never latched on. Perhaps (in addition to so much else) the poor reception of the prequel trilogy can be attributed to a simple disconnect between events on the screen and events outside. They really did feel like something a long time ago, but not in the way anyone wanted.
There is a direct comparison with the Lord of the Rings trilogy, whose first film premiered three months after 9/11. That trilogy found success in no small measure because it worked as a prism through which Western audiences could evaluate their newly fragile world. (The second part was even called The Two Towers.) Yes, principal photography had wrapped in 2000, and the novels were first published in the 1950s. But in theaters, audiences were imbuing the films with meaning and finding favorable comparison with events of the day. Here we had a nebulous evil thrust upon an unsuspecting group, and a consequent hard task and eventual obliteration of innocence. Sometimes the evil caused otherwise good people to do terrible things. And the world as masterfully portrayed by Peter Jackson was cold and challenging. The Lord of the Rings was dark, unrelenting, and very serious.
None of those things can really be said of Star Wars, whatever Lucas wants us to believe. Not for a moment would any clear minded moviegoer point to a screening of Attack of the Clones and say, "Geonosis is just like Afghanistan!" Rather, the prequels told a perfect story for the 1990s, when war was pretty much entirely bracketed by the imaginations of filmmakers. Obviously Lucas couldn't have foreseen the catastrophe about to engulf the planet, and so his story derailed. Later planning and regrouping wouldn't necessarily have helped—Lord of the Rings, certainly, would have been diminished had it been conceived and filmed as a statement on the War on Terror. The prequel story was simply incongruous to the times, however it was retrofitted.
With Episode VII, however, the disconnect may be righted. Already, we have a good idea of what the world post-War on Terror will look like. In lieu of big military offenses or visible progress, we have sanitized drone wars and covert actions. Gone is a monolithic enemy—that's been replaced by al-Qaeda, personified by Osama bin Laden. Here to stay are scores of loosely affiliated and undefined groups, each with its own goal. The horror in Benghazi might be a one-off, but it might also be a glimpse at the new normal. Gone is a president whose first act in office was directing the closure of Guantanamo; here to stay, whoever wins in November, are secret kill lists and four-part tests to decide when it's okay to assassinate American citizens.