So I was kind of twiddling around an idea inside my little head.
The opening premise does leave much behind, though personally it isn't necessary because the show should be focusing on the 'now' aspect but they could of had the General or someone explain to them what happened to the other assets or military forces around the world. It doesn't have to be in depth just something in an off the cuff remark, like the last stand of the Navy, desperate suicide missions of special forces armed with portable nukes to destroy enemy locations. Point being, a few words here and there can do wonders rather than to simply dismiss it as it was 'in the past' but it can also be used in a fashion of why they must fight in a certain way because the aliens had learned of the previous tactics, the motto of the resistance being, adapt, survive, fight.
Or we can all pretend we're in a Garnier advert and wave our long flowing locks of hair around.