The opening scene, depicting the Roswell crash of 1947 show an I-25 highway sign. The Interstate Highway act wasn't signed into law until 1956, and I-25 wasn't constructed until years after that.
When the soldier threatens to shoot the Doctor in the lab, he appears to cock his rifle as if it were a lever-action Winchester carbine, but US military rifles of the World War Two era and later were bolt action.
In the opening scenes, there is a shot of a sign for Interstate Highway 25 with the interstate highway shield logo. The caption says "New Mexico Desert, June 13, 1947". The interstate highway system wasn't created until June of 1956 and the shield logo wasn't selected until 1958.
The story takes place in the mid-fifties, yet there is an alien in a cell labeled "BIOHAZARD", a word which wasn't coined until 1973.
When the helicopter destroys the battle drone and lands to pick up the Doctor and Cassie and Jimmy, the soldier who talks to the doctor refers to Area 51 as Groom Lake Army Air Base". However, the story is set in 1958, and the US Army Air Corps/Air Force was separated from the Army to become the US Air Force in 1947.
The helicopter is a HU-1/UH-1 "Huey". The first HU-1 helicopters accepted by the Army (which were trainers, rather than operational aircraft) were not delivered until 1959.
The sign at the beginning says "Roswell 35 miles". I-25 (as it actually exists), according to Google Earth, comes no nearer to Roswell than about 140 miles.