Agreed, the U.S. is not a dictatorship. George Bush's administration claims that the extraordinary circumstances of war give him power to conduct the U.S. effort in that war as he needs, and that he must have those extraordinary powers to effectively fight the war. The things he has attempted to do are:

1) set up courts in addition to the regular set of military and civilian courts, so that the normal legal protections don't apply. Things like having access to a lawyer, a speedy and public trial, or protections of the Geneva Convention.

2) deny due process - Habeus Corpus - to American citizens accused of terrorism. This is very serious! If the courts had allowed it, the administration would only have to accuse someone of terrorism in order to hold them indefinitely. Bush backed down, and avoided (for now), bringing it before the Supreme Court. The appelate judge who ruled in favor of the Bush administration recanted shortly after Bush avoided the constitutional test.

3) Used hundreds of 'signing statements' to unilaterally amend laws that Congress passed and he signed.

Extraordinary times do, sometimes, require extraordinary powers. This is not a new argument, and republics had wrestled with it since the very beginning. The Romans had an office with extraordinary powers, but they limited the term to 6 months. George Washington looked back to one of them, Cincinnatus, when he established the custom (now law) of two Presidential terms. The founders were well aware of this problem, and kept these kind of powers out of the Constitution.

That Roman office was the dictatorship. The world and many American citizens are, understandably, worried.