In the U.S.A. there is no law that may prohibit a religion. There are many different confessions and ethnic groups, so there are a lot of festive days and traditions. The original US religion of most settlers was Christian Scientific Church.
Beside the Christians there are Jews, Moslems, Buddhists and some other little ethnic groups like Scientology etc.
In Wisconsin there are particularly Evangelists and Catholics, who have similar numbers of members. There are only very little groups of other religions.
The most popular churches in, or in the region of Port Washington:
St Paul Lutheran Church
St John's Lutheran Church & Academy-Missouri Synod: Church Office