The Reformation had several significant impacts on Europe. The correct options that apply are:
C) Religious unity in Europe came to an end.
D) Religious rivalries developed in the Americas.
A) Catholicism was not reinforced; rather, the Reformation challenged the authority of the Catholic Church, leading to the rise of various Protestant denominations.
B) The Reformation did not lead to a long period of peace; instead, it often resulted in conflicts and wars, such as the Thirty Years' War.
Therefore, the correct answers are C and D.