There are many different “themes” that could be identified in the history of the USA in this period. Here are four, inter-linked ideas. Thinking about the course thematically in this way may help you to see connections and patterns that you have not spotted before.
The rise and fall of the "New Deal order".
This is not just about the ascendancy of the Democratic party between 1932 and 1968 (although electoral politics certainly serves as a useful barometer here) but in a broader sense it is about the development and then collapse of a political consensus which favoured the expansion of government to aid working people and provide economic security.
How deeply embedded was such a consensus in the US? When did it begin to unravel and why? Think particularly about the differences between the New Deal and the Great Society: was there a shift from the principle of taxing the few to benefit the many to policies which could be portrayed as taxing the many to benefit the few? Which groups in American society supported the New Deal order and why did they turn against it?
At the heart of the New Deal was the claim that government could be used to benefit the people as a whole. How was this faith in government created in the first place and how and why was it undermined? What, for example, was the role of the Vietnam war and the Watergate scandal and what was the impact of media reporting of politics on public trust in politicians and government?