I'm going to say pretty confidently that it is not from a real film (from the golden age of science fiction), because it contains elements that cannot plausibly have been created at the same time.
The flying saucer has an absurdly retro Art Deco look to it, which probably would have looked dated rather than futuristic by the time of the first reported "flying saucer" sighting in 1947. It is basically inconceivable that a science fiction film would be using a design like that in the late 1960s or after. The creators of the commercial presumably selected the Deco styling on purpose—not because it conveyed any specific period of science fiction, but simply because of its retro, raygun Gothic esthetic.
In contrast to ship, the image of the Earth (before it is destroyed) cannot have been created before 1967 at the earliest. (The explosion also does not look like anything I have ever seen in a 1960s or earlier film, but that's trickier to quantify.) That kind of imagery of the planet's surface (you can see the Etosha pan, a system of salt flats in northern Namibia, for example) was not available until 1967. The first terrain images approaching the level of detail shown were taken by the ATS-3 satellite, launched in November of that year.
(ATS-3 was in a geostationary orbit over the Western Hemisphere, so it could not itself have taken that kind of image including of Africa, but similar views of the whole globe quickly became available as more satellites, from the ATS series on onward, were launched.)
In light of these temporal incongruities, I conclude that the shot of the aliens destroying the Earth is not from an actually classic science fiction film, but is an entirely modern creation.