That's an extremely broad topic. While you may still be able to address it, you should think about ways of doing it other than trying to find sources about that topic as a gigantic, general whole. Maybe look at acceptance of cultural differences from the perspective of
-changing perceptions of black culture throughout American history (while this is written about ad nauseum, it changes constantly with starts and stops, so the perspective is perpetually changing)
-comparing/contrasting the assimilation of different immigrant waves - you can start the whole way back at Scots/Scotch-Irish in the colonies, through Northern Europeans and Germans in the early 19th century, Irish in the mid 19th, Southern and Eastern Europeans in the early 20th, Mexicans in the late 20th/early 21st, etc., or just pick a few depending on paper length
-comparing/contrasting the concerns and strategies of the Know Nothing Party, 19th century Democrats, 20th century Republicans, etc.
-comparing, even more broadly, the acceptance of counterculture movements with each other and maybe with foreign cultures foreign cultures for fun?
Now I have to choose a topic relating to groundwater geology that isn't related to the depletion of California's aquifers or contamination around here due to fracking, like everyone else is doing
