When Peggy visits her son's room, she finds a stuffed bear toy in his bed. Such toys did not exist in 1880, the original "Teddy" bear being created in 1903.
The Van Rhijn servants discuss a recent European conflict in which families fought against each other, and how that could never happen in the USA. The American Civil War is in living memory during this time period, many families fought against each other in that conflict.