i’m not exactly sure how you make the leap from 'therefore, any single state or non-state actor that finds itself at war with the United States will be forced to fight an asymmetric war. That is, it will be forced to employ terrorism’ to 'therefore the war on terrorism is a war against anyone at war with the United States.’

I take issue with this on two different fronts. first, there are various asymmetrical tactics other than terrorism. in its classical concept, 'terrorism’ is the use of violence so that the psychological impact, or terror, is disproportionately larger than the physical damage. Detonate a dirty bomb in DC, it kills 50 people but terrifies millions. This is what separates 'terrorism’ from other combative techniques, such as guerilla warfare or kidnappings.

Second, there can be a large variety of wars between the US and other entities that do not fall under the ‘war on terror’ label. Possible conflict with Iran or Russia for example.

In terms of defending US imperialism, I don't think it's any surprise that conflict between the US and her enemies is always about economic interest or national security. Whether you’d like to call this ‘US Imperialism’ or ‘national defense’ is up to you…

The war on terrorism is a lie because terrorism is not an enemy, it is a strategy.
Terrorism is a strategy employed by weaker states and non-state actors when fighting an asymmetric war against a more powerful opponent.
No state or non-state actor enters a conventional war against an enemy it has no chance of defeating conventionally.
Since the U.S. has declared that it will maintain military superiority without challenge, it has done everything in its power to do just that. The US defense budget for 2008 is some $700 billion. There is no single state or non-state actor on this planet that can defeat the United States in a conventional war.
Therefore, any single state or non-state actor that finds itself at war with the United States will be forced to fight an asymmetric war. That is, it will be forced to employ terrorism.
Therefore the war on terrorism is a war against anyone at war with the United States. Therefore the war on terrorism is a lie. It is not a war on terrorism at all, but a war to promote and defend US imperialism.