Well, technically US is two parks - Universal Studios and Islands of Adventure. We typically do both parks in one day, so I think you could easily do one park in that period of time, especially if you get their Xpress pass. That is similar to the Disney Fast Pass, except you pay for it upfront, and you can automatically go to Xpress lane for any ride, no waiting for your time to come up or anything like that.
I think your daughter might be too young to go on most of the attractions at the Universal Studios park, but Islands of Adventure has a Dr. Suess land, with many kid's rides. They also have the new Wizarding World of Harry Potter, if anyone if your family has any interest in that.
Here is the link to check out all the rides at Islands of Adventure:
http://www.universalorlando.com/Amusement_Parks/Islands_of_Adventure/islands_of_adventure.aspx