There are differences. And of course, modern technology makes situations a bit different, but it was the similarities I was pointing out. We aren't having civil wars, but we've had that war in the Middle East how long? I was in high school when it started. What's our national debt now?
I really love it when people say we need to study History to learn from it, but ignore what's right in front of their faces out of arrogance. Modern technology and Science won't save shit. Each and every single empire that has ever fallen had the best technology of the time. Did that save them? When a nation tries to do too much at once, or extend its influence too far, it's doomed to implode eventually. It may not happen in the near future. We might limp along for a while longer. We might even see a little recovery for a short while. I don't know when, or how, but it's coming. If History teaches us nothing else, at the very least we should learn that nothing is forever.
Technology changes everything. You can bet that if the United States ever falls apart (and it most likely will) what happens in the aftermath will be very different than what happened in the waning days of the Roman Empire. The existence of Atomic Weaponry pretty much assures that. If you thought what happened when the Soviet Empire collapsed was bad, just wait, there was another world power around to keep some semblance of order with the defecting Nuclear Scientists and Russia managed to contain things to some degree. If America ever evaporates, I'd be worried about them taking the rest of the world with them.
But back on topic... Our pressing problems aren't like those the Roman Empire faced. The energy crisis, reigning in environment devastation, breaking the health care cost curve--all of that can be solved or at least lessened by potential technological advancements. The ideas are out there too, it's just a matter of waiting for them to be harnessed by the best and brightest amongst us. One thing no one seems to realize, is that problems are not solved unless they reach a certain threshold of danger where tolerating the status quo is no longer an option.
Relying on oil was always a pain in the ass, but it wasn't until the price got gouged ridiculously several summers ago that searching for a solution to the energy crisis became in vogue politically again. At the time there was a magazine (I want to say Wired) with a cover of a smiley face made from oil and a caption beneath it that read something like, "How an increase in oil prices is good for America." The editorial explained that unless we reached a certain point of expense, people would be complacent and willing to continue playing substantial amounts of money (in deceptively small installments) to dictatorships and nations with questionable allies. Once it becomes a large enough problem, then the willpower to solve it will amass and research to do becomes more economically viable.
Looking through this prism, it isn't at all surprising that the United States hasn't solved much of anything since World War II, because since then, our problems have been relatively few. You may say the Vietnam war was a big deal, well lets take a quick look at statistics from that era:
Total of US Armed Forces Worldwide: 8,744,000
Deaths from the Vietnam War: 58,236
Injuries from the Vietnam War: 153,452
This comes out to around 2/3s of a percent of our Armed Forces were killed in Vietnam, and the total number of wounded plus killed comes out to less than 3%.
Now lets take a look at the Iraq War for some perspective:
(as of May 28, 2010)
Total number of US Armed Forces: 3,385,400
Deaths from the Iraq War: 4,404
Injured during the Iraq War: 31,827
This comes out to around 1/9 of a percent of our armed forces killed in Iraq (and by the way we have a hell of a lot fewer than we did during Vietnam), and about a percent for the total number wounded and killed.
Both sets of numbers reveal that the wars we've gotten ourselves into really weren't that costly, and things aren't anywhere near as bad as people think they are. America has been complacent because times have been good. They've taken a bit of a turn for the worse, but think of it is an auto-correction in the timeline of our country to get us back on course.