This is, of course, purely a matter of personal opinion. My own view is that Catholicism was largely a force for good because it generally served to mitigate in some ways the evils that were done to the natives of the Americas. It is my view that the bad things that were done in the name of Catholicism would have been done even if the European Catholics had been secular (or if they had been Protestant) and that Catholicism served to humanize the Europeans to some degree.
It is true that Catholicism was used to help justify atrocities in the New World. The Spanish believed that they had a God-given right to dominate the New World. This meant that anyone who opposed them was also opposing God. Because of this, they could use their Catholic religion to justify savage suppression of any opposition to their rule. The Spanish missions in what is now California used Catholicism to justify abuses against the Indians there. These facts can lead us to say that Catholicism was not a force for good in the New World.
However, I would argue that the abuses were going to happen no matter what. My main evidence for this is that Europeans who were not Catholic were just as likely to abuse Native Americans (and Africans) as Catholics. English and later American Protestants were quite willing to kill Indians simply to get their land. English and later American Protestants were willing to enslave Africans for economic gain. This seems to indicate that it was the Europeans’ greed for wealth and power, and not Catholicism per se, that led to abuses.
I would say that Catholicism was at least to some degree a force for good. Catholic clergy in Spanish America sometimes tried to force secular authority to be more humane toward the natives. The Catholic clergy had to at least try to show that they were helping the natives while the secular authorities did not have to live up to any moral ideals. Catholics like Bartolome de las Casas spoke out against the abuse of Native Americans.
In this way, we can say that Catholicism was at least somewhat of a force for good in the New World. It was certainly used to justify evil, but that was evil that would have been done no matter what. Some Catholics used their faith to try to prevent abuses, thus making Catholicism a minor force for good.
This question is a matter of opinion, perspective and circumstance. In answering it you need to consider the perspective of several key groups- the conquistadors or explorers who went to the "New World", the indigenous groups they encountered when they arrived, and the Church itself. You also should consider whether or not you believe expeditions to the "New World" we're inevitable, and to what extent the Church motivated these expeditions. Last, weigh these perspectives and the circumstances to form your own opinion, remembering that this is a very complicated issue that terms of simple good and bad might not cover.
Spanish and Portuguese explorers came to the so-called New World for a wide variety of reasons, with many of them believing it was their God-given task to convert all peoples in the world to Christianity, and in the case of the Spanish and Portuguese this meant Catholocism. It could, therefore, be argued that regardless of the Church and its representatives actions once they reached North and South America, that as a motivating factor for the exploration and conquest of the land and indigenous people, they couldn't be a true force for good. Unwittingly, the belief that God wanted Europeans to spread Christianity in part led to the spread of smallpox to the indigenous people of North and South America, which decimated their populations.
On the other hand, you could argue that without the checks put in place by the Church and individuals within the Church, Spanish rule had the potential to be far harsher and more punitive. Many priests, for example- the very vocal Bartolome de las Casas, spoke strongly against Spain's use of the indigenous people as slaves. He wrote forcefully aGiants what he saw as Spanish abuses of the indige people. However, he also advocated for instead using African slaves to fuel "New World" colonial ambitions.
The Church itself may argue that the large number of converts, and today the large portion of South and Central America that are Catholic are proof that they have been a force for good. The acceptance of the Church's message by so many generations could be seen very positively by the Church. However, that doesn't take into account forced conversions of many groups and individuals.
Overall, as long as you support your side, there isn't a right or wrong answer to this question. What is most important is to let your reader see how you came to your opinion.