First, let's clear up a misconception. Films don't normally "come out on the same day". It is more common for this to happen nowadays, but many films still have several weeks or months between American release and European/worldwide release. (10 years ago, in the UK we had to wait 6 months in most cases.)
There are several reasons why films are released at different times, including cost, negotiating distribution rights and local sensitivities. Some of this is answered here: Why is international distribution so tangled even for recent movies released first online?
In the specific case of Wreck-It Ralph, movies targeted at children are usually released to coincide with school holidays to take advantage of daytime showings. It is currently "half-term week" in the UK (some schools last week, some this week) so it was released last week to maximise attendance.
If Wreck-It Ralph was released last November in the US I suppose it could have been released in December to take advantage of the Christmas holidays, however I believe cinema attendances are lower during that period (as people prefer to stay at home or are busy visiting relatives).