This is an important question because it is a hindrance to many. I am not very familiar with the history of the US but will answer this from an Indian perspective.
This is a very common sentiment in India, which parallels the situation in North America and Africa. The common refrain is this - the Christians (British) came and destroyed India by subjugating native Indians and looting India’s wealth.
The problem with this line of thinking is this - the white man or foreigner from Europe or America is automatically equated with Christianity. So when the British came purely for selfish trade-related reasons, to make more money for the empire, it was interpreted as the work of ‘Christians’. Why? Because the British built churches for their own people, they dressed differently and separated themselves for the ‘lowly’ natives. The reality was that these people had no Christian motive at all, they ruled merely for profit.
On the other hand, when genuine Christian missionaries came to India to bring the love of Christ to the natives, the British (and the Dutch) actively discouraged them and were opposed to their activities. When William Carey landed in India, he faced tremendous opposition. When Dr. John Scudder (first medical missionary) landed in Calcutta, he was not allowed to go in. However, these intrepid missionaries persevered and the service they rendered to the country still continues to bear fruit today - whether it was education, health, hospitals, women’s rights, translation of scriptures, making scripts for local languages…the list goes on.
I think it is the same everywhere, whether in the Americas or Africa. This is why I like a statement by Ravi Zacharias - “One does not evaluate a philosophy by its abuse, but rather by the logical consequences of what it leads to.” (paraphrased). Many have abused Christianity, whether it was for the Inquisition or empire building or waging wars. In many cases, Christianity was wrongly attributed to the oppressors as being their identity when this was not so.
Evangelism, properly understood, is a tool for sharing the love of Christ, his redemption, and not for personal agendas. It can be evaluated and understood only based on the Bible and its mandate, not based on popular perceptions, personal opinion and interpretations of history. It requires patient dialogue to make this clear to those who have this question.