I'll gladly take a shot at this question, but I hope that others will chime in, too.
What strikes me first when I view the painting is the division of the image into two halves: on the far right side is a building (maybe a house, made of wood with a stone fireplace), while on the far left, in a position opposite to the building, are the trunks of one or two pine trees. This division is continued with the positioning of people and furniture in the painting. To the right, with the building, are the newly arrived white settlers, dressed up and with little skin showing (mostly only their pinkish hands and faces). These people also have a table and chairs. Opposite them are the native Americans, seated on the ground or on blankets while they talk or eat. Two of the men in this group have bare shoulders and chests, and their skin is noticeably darker than that of their Puritan neighbors. At the same time, of course, there are smaller details that work against this simple division into two wholly separate groups. One of the native Americans, for example, wears a European-style hat, and several white people appear in the background on the left side, talking among themselves or talking to one or more native people.
The net effect of the painting, to me, is to show the peaceful interaction (with the meal, with the implied trading, etc.) between two groups of people. This may be a simplisitc view of the painting, however. The technological achievements of one group are shown, but those of the other group are not (American Indians of the northeastern regions did have houses. used tools, had complex social networks, etc.; they didn't sleep under pine trees!).
When I continue to try to see how the painting might reflect Western bias, I also notice that the trees in the background have more shadows than the building and that the smoke of the fire seems almost to bellow forth from the native Americans themselves. The opposition of light and dark has been widely used in early, culturally biased representations of the New World (see, for example, Mary Rowlandson's capitivity narrative or Phyllis Wheatley's poem "On Being Brought from Africa to America").
This question has been asked before. Check the link below for more discussion of the painting.