Take Falling Skies for example with its basic alien invasion/occupation storyline, you have a standard insurgents versus technological superior asymmetrical warfare scenario, the twist being that the Americans are the technologically inferior insurgents! What struck me watching the programme is how easy it would be to re-use Modern troops and survivor miniatures from zombie games against SF models. With them you do not need to specifically re-create the aliens out of Falling Skies, I think any futuristic SF types could be used, especially anything with walkers, maybe even Eldar.
Alien invasion stories such as Independence Day or Turtledove's World War book series show that modern (or even WW2) regular forces can be used to fight alien invaders in pitched battle, and even if the human equipment is inferior, as Stalin said "quantity has a quality all of its own". Taking Turtledove's background, the Race were small four foot tall lizards so 15mm SF armour can be used against 20mm WW2 collections.
Of course, as Turtledove has done, there is no reason why alien invasions have to occur in this time. Turtledove used WW2, but the film Outlander pitched Vikings against a Predator like foe and of course there is the more recent Cowboys v Aliens. Really the only limit is your imagination and your miniatures collection, asymmetrical warfare does not just have to be the Taliban against NATO...
Gromit of the Day: