What are the similarities and differences in social structure and culture between 17th and 18th century American civilization?
It's a great question, but also a very large topic to cover in the space we have here. I would say the main similarities between the 1600s and the 1700s in terms of American society included the fact that we were an agrarian society of mainly small (yeoman) farmers, and that society in both the northern and southern colonies had a small, white, mostly English class of wealth, privilege and power. This did not really change until the 1800s, and then only slowly.
In terms of differences, I would focus on the rich cultural and ethnic diversities that emerged in the 1600s, but grew and multiplied in the 1700s. In the 17th century, English, Irish and Scots more or less dominated the landscape, with a small number of African slaves. By the 18th century, larger numbers of Germans and Swiss, Dutch and French (and slaves, particularly in the Carolinas and Virginia) and growing interaction with the native populations all led to a more diverse culture overall.
In terms of social structure, very little changed in these two centuries. The pecking order of society stayed the same with planters and aristocrats followed by merchants, lawyers, doctors, professionals, then a huge number of small farmers, indentured servants following them, and slaves at the bottom. Women were considered second class citizens with little status and few rights.