As Ronald Reagan noted,
Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same, or one day we will spend our sunset years telling our children and our children's children what it was once like in the United States where men were free.
That's true of freedom, but it's also true of values, wealth, power, and influence. There's absolutely no guarantee that future generations of Americans will grow up in a prosperous, free super power as we have. In fact, it's entirely possible that America could be a terrible place to live a few decades from now. Of course, that doesn't have to be our future either. If we are smart enough to learn from other nations’ mistakes, we can avoid their fates.
1) The Soviet Union: In the sixties and seventies, many economists believed the Soviet Union had an economy that was superior to ours. In fact, when Reagan came into office, many economists still expected the Soviet Union to eventually surpass America economically. Reagan knew better and realized he could break the Soviet Union economically. He dramatically ramped up American military spending because he knew that the Soviets couldn't afford to keep up with us. Reagan also convinced Saudi Arabia to help reduce the price of oil, which sliced into Soviet revenues, told Europe not to buy more oil or natural gas from the Soviets than absolutely necessary, and helped enmesh the Soviets in an expensive war in Afghanistan. Then Gorbachev, in an effort to save the Soviet Union, started giving the people more economic and political freedom, which spiraled out of control and led to the downfall of the Evil Empire.
Today, America is relying on nations that don't have our best interests at heart to provide us with the oil we need to power our economy and to buy our debt. Could America handle another seventies-style OPEC oil embargo? Could we deal with an organized effort to convince other nations not to buy our debt? Imagine going another half a trillion dollars deeper in the hole every year just to finance our debt. How long do you think we could keep that up, especially on top of the out-of-control spending we already have?