Though the major religion in America is Christian, there is no official religion or established church that is supported by the government. Indeed, strong efforts are generally made to prevent any open governmental support for religious activities of any kind. The doctrine of "separation of church and state" is widely respected, and perceived deviations from it over such matters as prayer in public schools cause vigorous debate. Religion is generally considered a private matter. People have their own beliefs, and they may or may not discuss them with others. Americans are generally taught not to raise the subject of religion with people they do not know well, so they will not offend or create an argument with someone who has differing views.
Visitors from abroad will find a wide range in the religious practices of Americans in Iowa City. Some people here attend a church, synagogue or mosque weekly and also participate in related social and service activities. Some attend irregularly, perhaps no more often than once or twice a year. And some do not go to church at all, perhaps because they do not believe in Christianity or because they do not believe that "organized religion" adequately represents their own religious or philosophical beliefs.
Some of those Americans who openly discuss their religious beliefs belong to fundamentalist Christian groups who consider it their duty to try to attract others to their faith. Or they may be members of "cults." These groups often single out international students and try to “convert” them to their own religious views. International students will want to be aware that kindness done them or interest shown them by representatives of religious organizations may be displays of genuine helpfulness and concern, but may also be part of an effort to induce a student from abroad to join a fundamentalist group.
Iowa City has many churches, both Catholic and Protestant. There is a significant Jewish population here too. The names and addresses of Iowa City churches are in the yellow pages of the telephone book under "churches." The listing is classified by denomination. There is also a yellow page listing of synagogues. At http://www.yellowpages.com/iowa-city-ia/religious-organizations is another listing of religious organizations in Iowa City and Coralville.
You can also find a religious or spiritual student organization on https://orgsync.com/home.
Many churches have "campus ministries" that pay particular attention to the religious needs and interests of university students. The Association of Campus Ministries is a confederation of campus ministers of various denominations.
Foreign Visitors and Religion
Foreign students and scholars who are Christian or Jewish and who want to join a church or synagogue here can simply look up appropriate addresses and telephone numbers. Those following other faiths can seek out fellow nationals who share their beliefs and ask how they go about practicing their religion in Iowa City.
If you want to see what happens in an American church you can simply attend a service. Or you can go with a friend or acquaintance who attends a church or synagogue.
If you meet a fundamentalist Christian who tries to persuade you to join, you can simply say that you are not interested. You need not listen or reply to a person who does not appear to respect your right to have your own religion. One tactic proselytizers (that is, people who seek converts from one doctrine to another) use is to invite international students to "a dinner" or "a party" or some other event without informing students that the event is sponsored by the church and that those who attend may be subject to pressure to change their religious beliefs. Students who find themselves in such situations can simply leave if they are uncomfortable.