So we know Cage gets the ability to reset the "day" by absorbing the blood of an Alpha mimic thus enabling him to kill the Omega and end the war. That's cool and everything but what happens to everyone else? We know the day resets for Cage and that begins a new loop but does that mean events in the loop that he just died in continue? Meaning that for everyone else the invasion fails and Britain is overrun since the whole thing was a trap to draw in the bulk of the UDF'S forces. Or does the day reset for everyone else but they don't have any memory of what just happened or what's about to happen?
It depends entirely on which theory of time travel the story is operating under, something that may, or may not be explained in the original source. However, I'm going to go out on a limb and assume that the theory under which the story is operating is a single universe with no time-line branching.
I'm making this assumption mostly because under the multiverse theory (used in a number of stories including Time Trax and Source Code), the constant resetting of time would leave behind countless broken universes, which seems contrary to the intent of the story - that the main character will be able to Fix Things. The same would also apply to a branching universe theory of time travel.
If there is a single universe with a re-writable history, then the answer is the second option given - time is reset for everyone and only those who are stuck in the loop have any idea of what is about to happen, or that they have repeatedly relived that same day, etc.
As @FuzzyBoots pointed out, the reset in question is a complete erasure of the entire time that passed during the period that was reset - that time never passed, those memories never existed. The exact mechanism allowing Cage's character to remember what happened isn't explained in the movie. In the book, apparently, it is clear that the information about previous loop iterations was transmitted to his mind when time reset, and that the character didn't actually "relive" that time, he only remembered living it previously.