Iraq and Afghanistan are pretty good examples that even though the former regime might not be popular people will rise up against foreign invaders.  The same can be said about Iran.  While their regime is on a fine line with their people, it is widely believed that they would back their regime if invaded.  So the best possible solution would be to let Iran work its own problems out on their own without foreign intervention.  However, Syria has been left alone and a lot of people have died trying to rise up against their regime. 

Would you join the resistance to fight off foreign invaders even if your previous regime was deemed evil?

Depends on if our Military would need civilians to help.

I would prolly do my best as paramedic outside of the military forces/resistance... but I would prolly support the resistance. I wouldn't engage a fight though. There is no gain in killing someone.

Yes, and I'd bring my own weapons.

Depends on who invades and why

Not after what happened to Nathan Hale.

Don't lie!  I heard you keep your Army uniform ready at a moments notice.

I'd join the resistance because unlike the countries you listed, mine doesn't need to get liberated from anything.

If the state of affairs were different, and I was against the current regime, I wouldn't of course.