While most of the people who came to America in colonial times were Christians, we cannot say that all of them were. Therefore, we have to say that this statement is false.
It is true that most of the people who came to America were Christian. This is particularly true of the white Europeans who came to America. After all, Europe was heavily Christian at this time. However, it is not true that all Europeans who came to America were Christian. Instead, we have to remember that some of the colonists were Jewish. Jews did not come to America in large numbers but, as seen in the link below, they were present.
A larger source of non-Christian colonists was Africa. Africans were, of course, brought to America against their will, but they were still a major part of colonial America. The Africans who were brought as slaves were not Christian. Many believed in animistic religions while others were Muslim.
We tend to think that all the people who came to America in colonial times were Christian, but this is simply not true, particularly when we remember that not all the people who came to America in colonial times were white Europeans.