The U.S. Declaration of Independence states that "when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government”
You must also remember that the Supreme Court can and will stop this law from happening.
If anything bad happens we can exercise this right. This is what solves your worst case scenario. There is also the fact that unlike countries that have/had a dictatorship, there is no party that has complete and utter control over the United States of America. What happened in Germany is that the Nazi Party took over and signed something that gave Hitler complete control over Germany. America does not have that party.
More Stuff:
New Hampshire's constitution guarantees its citizens the right to reform government, in Article 10 of the New Hampshire constitution's Bill of Rights: Whenever the ends of government are perverted, and public liberty manifestly endangered, and all other means of redress are ineffectual, the people may, and of right ought to reform the old, or establish a new government. The doctrine of nonresistance against arbitrary power, and oppression, is absurd, slavish, and destructive of the good and happiness of mankind.
Other States have something similar to this in their Bill of Rights.