What did pastors in the 1800s in the United States teach their congregations about interacting with Native Americans?

Christian pastors responded in diverse ways to the issue of how native Americans should be treated. This article summarizes:

Among whites there were two common religiously based attitudes toward Native Americans. One was expressed in the notion of Manifest Destiny, the idea that white Christians had a God-given mission to expand their civilization and its ideals of liberty and democracy across the entire North American continent. From this point of view Indians who occupied valuable lands could be removed or even exterminated with few moral qualms. A second point of view held that the Indians did not have to be seen as a hindrance to white progress. Rather, they were simply ignorant heathens who could become part of American society if they were allowed to benefit from the civilizing instruction of whites.. Although earlier missionaries to the Indians had produced few converts and much antagonism, the revivals of the early nineteenth century brought new impetus to the missionary movement. Most Protestant denominations as well as the Roman Catholic Church sent men and women to Indian tribes across the country, where they preached, distributed Bibles, and established schools.

It should be added that few if any preachers supported intermarriage between Whites and Native during this period. Also, preaching varied regionally and depended on recent events.

Manifest Destiny

Although he was a journalist rather than a pastor, the views of John O. Sullivan were extremely important among Christians who believed the Native Americans need to make way for American expansionism:

John L. O’Sullivan (1813–1895) preached a particular form of Christian nationalism that centered on expansionist fever occurring during the 1830s and 1840s. O’Sullivan’s Christian nationalism was known as “Manifest Destiny”. He famously coined the term in 1845 while defending the right of the United States to annex the Republic of Texas... As a form of Christian nationalism located in the context of antebellum America, Manifest Destiny is helpful to historians as they trace both continuity and change over time in how Americans have self-identified in religious terms since their origin as a collection of colonial, and later independent, polities.

Christian Opposition to Indian Removal

The Second Great Awakening provided examples of preaching that supported the rights of Native Americans to remain in their lands.

Evangelicals proclaimed that the Cherokee were becoming “civilized,” which could be seen in their adoption of a written language and of a constitution modeled on that of the U.S. government. Mission supporters were shocked, then, when the election of Andrew Jackson brought a new emphasis on the removal of Native Americans from the land east of the Mississippi River. The Indian Removal Act of 1830 was met with fierce opposition from within the affected Native American communities as well as from the benevolent empire [supported by Evangelical preachers]. Jeremiah Evarts, one of the leaders of the American Board, wrote a series of essays under the pen name William Penn urging Americans to oppose removal. He used the religious and moral arguments of the mission movement but added a new layer of politics in his extensive discussion of the history of treaty law between the United States and Native Americans...

Anti-removal activism was also notable for the entry of ordinary American women into political discourse. The first major petition campaign by American women focused on opposition to removal and was led (anonymously) by Catharine Beecher... Beecher called on women to petition the government to end the policy of Indian removal. She used religious and moral arguments to justify women’s entry into political discussion when it concerned an obviously moral cause.

Salvation and the Savage by Robert F. Berkhofer Jr. deals with the Protestant missions to the natives in detail.

For Catholic attitudes I found this book on California History helpful, although it deals only with California.