The USA international scored on his debut for United in victory at Bolton, and made 17 appearances for United in total.
Blades boss Chris Wilder said: "We thank Cam for his contribution in the first half of the campaign and Spurs for loaning him to us - we hope both feel the loan spell was beneficial."
The 20-year-old, born in Southend, earned He earned his first full cap for the USA in November.