First would be the 42 month reign of the Anti-Christ which is mention in the bible (revelation chapter 13), most people especially Americans seem to equate this with the 4 years President Obama will be serving as U.S president. I don’t think this theory is even plausible because 4 years is equal to 48 months and a 6 month margin seems to be pretty big error for a prediction that could effect the lives of everyone in the whole world. The next theory involves the year 2012 and the Mayans. According to the Mayan calendar the world as we know it will end on the year 2012 and coincidentally President Obama's term as U.S president will end around that time, however many people are mistaken on this as the Mayan calendar clearly suggests the end of an “age” wherein another age will begin and not the total destruction of life by an evil entity we fondly refer to as the Anti-Christ.
If we strictly based our beliefs on the end of the world from the mayans point of view, then we should be rejoicing when 2012 comes, as the mayans also suggest that the next age will bring forth enlightenment and wisdom to the human race which will result in an age of peace and prosperity.
Perhaps the real reason why Americans and for that matter the whole world would entertain ideas like this is because most of us yearn to live in a world where everything is dangerous, exciting and full of mysteries. People around the world hope their lives could be something more than what it is and so they easily believe things that they think could make the world a bit more interesting and adventurous.