When the Master stands up on the Valiant to announce his that he is "the Toclafane's Master", President Winters is visible in the background, only the Toclafane aren't there. In the next shot, they return, buzzing around Winters' head.
Winters is described as "President", but identifies himself to the Toclafane as "President Elect of the United States of America". The President Elect is the candidate who has won an election (in early November) but not yet taken office (on January 20); he has no authority yet. (Russell T. Davies has stated that he used the term President-Elect without realizing what it actually meant, and that Winters is meant to be the full President of the United States.)
Right after the Doctor, Martha, and Jack time jump back to present-day England, Jack walks down the street with his handgun openly visible on his hip. Considering England's strict gun laws, it's unlikely someone wouldn't have called the police and reported him.
It's stated that by the time of the events of Doctor Who: Utopia, all the stars had burnt out. When the rift opens to the end of the universe to allow the Toclafane to come to the present day, stars are visible on the other side of the rift.
When the police open fire on Martha's car, you can see sparks where the bullets from their guns bounce off her windscreen. At that close range, just one of those bullets could go through a brick, and despite the back window of the car being shattered, there are no bullet holes in the sides of the car, nor have the side windows been shattered.