The first time Jack googles The Beatles in his room, there is a Killers poster on the wall behind him. The Killers were formed after their lead singer Brandon Flowers was inspired by an Oasis concert he had attended. Later in the movie, it is established that Oasis, in addition to The Beatles, had been wiped from existence as a result of the blackout. Therefore, The Killers would likely not exist as well because Brandon Flowers would not have attended an Oasis concert. Response: There is no way to know if The Killers would have been created if Oasis did not exist. In the alternate reality that movie creates, Brandon Flowers would have been inspired to form a band while watching a different concert.
In the film, Jack and Ellie remark multiple times about the time in middle school where Jack played "Wonderwall" at a talent show, and that was the moment where their friendship blossomed. However, the band Oasis (along with Coke, Cigarettes, and Harry Potter) is one of several well known entities to be non-existent in the alternate world. This means that Ellie would not have any idea what the song "Wonderwall" is.
The goof item below may give away important plot points.
Following Jack's rise to success, many eager screaming fans chase him in public places. Yet there are plenty of scenes after this point where no one chases him/seems to notice him (his dining in an upscale hotel restaurant seems to be the best example of him being "ignored").
The bus which hits Jack should never have hit him. It clearly drives over a road marked GIVE WAY triangle the driver would have seen before the lights went out. Also, if the driver knew the route, he know there was a give way sign there already, lights or not. He should have been slowing down to stop at the junction.