Where I live, the way contract law (at least in regards to employment) works is generally you can't alter terms (by imposing additional restrictions) after both parties have agreed to it unless there is some form of compensation provided for the restricted party in exchange for agreeing to those additional restrictions.
EULAs are a magical playground in USA. If you agreed in initial terms that they can change this document in future with or without notifying you, then they are within their rights to change it.