1) Illegal aliens. About 30-35 million of them, suppressing wages and straining the social welfare net. If there were about 1-2 million illegals in the country, most of us would not notice them.
2) Obamacare and the ripple effect from that disaster. People actually do react to legislation, especially tax legislation, that affects business behavior, and the cost and taxes related to Obamacare is messing with our economic growth.
3) John McCain. I don't feel the need to expand on that, since so many Freepers can wax much more eloquently on the subject. Summary; when that obstacle is gone, America can be back on the road to real recovery.
4. -- which really should be #1 because it has a bigger impact than #1 through #3 combined ... A demographic disaster with retiring Baby Boomers removing more and more people from the productive population.