I think that the movie should start with President Hayes starting to address the world and tell them about the Stargate, then the movie cuts to black, with a title reading "___ Hours Previously." After that, SG-1's part of the movie starts at the SGC, where SG-1 is having a briefing about a planet with Furling ruins before suiting up and going through the gate. As soon as they step through the gate, they get beamed down into an underground base and find a Lucian Alliance guy asleep on the ground. After waking him up, SG-1 learns that Kefflin took the Alliance after Netan was offed by that bounty hunter and made finding advanced technology a priority, in order to defeat the Tau'ri; as they try to find a way out, the Alliance guy mentions that Kefflin might have found an Ancient satellite weapon and managed to create a copy of its weapon for the Alliance's Ha'taks.
They find a Furling in a stasis module (the Furlings are similiar to anthropomrphized wolves) and accidentally awaken it; it holds them at gun point until Daniel tells it who they are, the Furling proceeds to awaken some more Furlings, before escorting one of the newly awakened Furlings to the SGC (where the Lucian Alliance guy is tossed into a cell). Mitchell and Teal'c head off to see if the Alliance does have an Ancient satellite, hitching a ride on a Ha'tak commanded by Rak'nor, while Daniel tells the Furlings everything that has happened since they went into stasis; in orbit of the Furling planet, a cloaked Tel'tac sends a message to Kefflin after detecting the Furling base power up. Rak'nor's Ha'tak exits hyperspace behind a moon and picks up the Ancient satellite, right before it fires; quick manuevering saves the ship from destruction, but most systems are fried, except for communications and sensors. Mitchell sends a message to Earth that the Alliance has the satellite and that a dozen Ha'taks might be heading to Earth.
Landry sends several SG teams to assist the Furlings awaken everybody in stasis, before having the Odyssey and Apollo take defensive positions in orbit of Earth. Four Ha'taks appear in orbit and two of them use cheap knock offs of the satellite weapon that do some damage to the ships' shields; they are easily dispatched by the Asgard beams. Then they find out that the Ha'taks were distraction, diverting attention from 48 cloaked Al'kesh that have been hiding behind planets and other celestial objects to avoid detection. Half head for the SGC and the others head for Washington DC; the Osyssey and Apollo split up and take on the Al'kesh over the cities in broad daylight.
Meanwhile, the other eight Ha'taks begin attacking the Furling base with ground troops and orbital bombardment. The SG teams fight off the Alliance foot soldiers that manage to get into the base, while the Fulings power up hidden orbital defense satellites and destroy the Alliance ships. Sometime later, SG-1 is informed that the Stargate will be going public and that they will have to go to Washington as part of the press conference at the beginning of the movie.
The movie returns to Hayes' speach, where SG-1, Jack O'Neill, and the Furling representatives come on stage. The movie ends with O'Neill beginning his own speech.
