What is the biggest obstacle we face in the 21st century?

From an American standpoint, our dependence on foreign oil is a bigger problem than our dependence on oil in general. We've got all kinds of oil and oil shale here in the States, enough to live on for many, many years to come without having to rely on getting it from foreign countries. Plus, fossil fuels are more reliable than the alternative forms of energy. And, fossil fuels are not the big threat to the environment that many of our politicians and environmentalists want to make it out to be. There is nothing wrong with using other forms of energy, but they will probably never be as reliable as fossil fuels and even if they can be more reliable, it will take some time to get to that point. We should tap into all the fossil fuel resources we have here. The way it stands now, other countries can come into our waters off the coasts and take the oil right out from under our noses, oil that is rightfully ours. The only other obstacle that might be greater is terrorism.