Question: "What does the Bible say about colonialism and imperialism?"
Answer: The Bible does not directly address colonialism or imperialism. There were of course empires in the times of the Bible, and, to the extent that they oppressed Israel and other nations, they were eventually judged. Amos highlights a series of judgments that will fall on nations who were oppressive.
Of course, colonies have existed from ancient times, but what we think of as colonization and imperialism are relatively modern practices. Imperialism involves acquiring new territories for a nation as it extends its dominion to other areas. The idea of colonialism is to put a group of people from the “motherland” into a new environment where they can carve out somewhat of a copy of the mother country and develop the natural resources of the new land. The colonies buy goods from the mother country and provide raw materials for the mother country. The colony is an extension of the mother country, and, as loyal colonies are planted around the world, an empire is born. There was nothing inherently wrong with this plan except that it often impinged on the rights of indigenous people who were already living in the colonized land. The most cynical view of colonialism is that indigenous people were simply exploited. A more benign view would say that the indigenous people did receive some benefit by way of trade and advancement in technology, and in many cases the gospel was spread. Colonization was often interwoven with missionary activity.
Unfortunately, many missionaries (but by no means all) united the gospel with their own culture, so what they spread was a mix of gospel and “Western civilization.” In many cases the missionaries were insensitive to what was good in the native cultures and treated the indigenous peoples as children who were unable to think and act for themselves and native culture as something to be irradiated. Even in these cases, we know that some people came to faith in Christ and will be eternally thankful for a missionary who, although not culturally sensitive, came to their shores as the result of colonization and imperialism. Today, evangelical missionaries are much more careful to study the culture they are entering and to allow for indigenous expressions of faith, without changing the essential message.
Our current “cancel culture” demands that we analyze and pass judgment on the acts of previous generations and then “cancel” those who are found to be guilty of violating our current societal and cultural mores. However, it is unfair to judge previous generations based on present-day ideals because to do so assumes that our current standards are correct for all times and all places; it is quite likely that a future generation will cringe at many of the things that are common practice for us. No doubt, some colonists had the best of intentions, and others were exploitative. There is simply no way to go back and sort it out or undo the sins of the past.
Governments today generally do what they think is best for their citizens, or, perhaps more correctly, government officials generally do what they think will be best for their careers, which in some cases is best for other citizens. Often what is best for one country will be detrimental to another. Christians in positions of power (and all other Christians, too) must keep in mind the commandment that “you must love your neighbor as yourself” (see Galatians 5:14). In most cases today, loving one’s neighbor would most likely not involve colonization or imperialism.