Though the illustration can be somewhat understood in any language (the helmets, the habit and the Indian aspects are universally recognized), it still helps to know what the caption says in Spanish: ”The signing of the first free trade treaty with Spain.”
Perhaps the message this pic wants to convey is that there is a strong resemblance between current free trade treaties and European colonialisms in the Americas. And this resemblance points toward an unveiled injustice sanctioned by supposedly benevolent institutions like the Church. The illustration serves as a warning to small-impoverished countries that the apparently friendly advances of more powerful countries (the entire courtship process, in fact) will lead to the same form of brutal submission.
Yet, though the picture is clearly (sensationalist) meant to impact with the unavoidable truth of the power behind unequal relationships, it is also deceiving, or better said, incomplete. It looks rather similar to the way that Bartolome de las Casas portrayed the interaction of Conquistadores and Indian, a mistaken intellectual legacy that we today call "The Black Legend."
The broader truth is that the Spanish Church struggled with the question of the Indian’s rights and humanity like no other European religious institution did until the 19th Century. It also produced a minority of vocal activists that worked for the betterment of the Indians’ condition—they proposed reforms, admittedly, full of shortcomings and bent to benefit the Church over Indian religiosities. But the point is that the Church’s role was not as simplistic as it is shown here.
Also, the Conquistadores and Spanish masters did not want to kill Indians indiscriminately. Instead, they wanted Indians alive and healthy, but submissive in order to have them as workers and servants. In fact, their idea for a social order among the Natives was a refurbished version of the European serf-like system. The main difference was that the Whites would be at the top of the hierarchy and the Indians would fill in the ranks below. So, aside from times of rebellion and conquest, they would not go around killing Indians; they would, instead, colonize them with oppressive institutions and laws.
The most problematic part of this pic, however, is that it shows Indians only as victims. There is no muscular or devilish-looking Indian; and the only one that is still alive is running away. The reality was that Indian forces fell more to the power of the new diseases than to European weapons. The little-know story of the Indian resistance shows that Indians were often more effective in their warfare than Europeans, and that they quickly adapted and even surpassed Europeans. Diseases, however, changed everything.
Not sure you need a translation for Colonialism.