I would assume the EMA has different forms, and wants the data in a different format. Pfizer as a US company presumably has more experience with FDA formats as well, and more FDA experienced people on staff (this is one of the advantages of the revolving door between industry and regulators - there are disadvantages as well).
I'm not sure why the UK got things sooner unless it is because they accepted data sooner there was time to figure out how to submit it while not even knowing if they would submit to the FDA.
