I think the modus operandi of the Democratic party is to shift blame. An example is slavery. Over the years and decades I have listened to, or read, several attempts to shame/blame America for slavery. In every instance the speaker was a Democrat. Sometimes southerners and whites are blamed for slavery. There is never an acknowledgement that the Democratic party was the slavery party. Democrats shift the blame away from themselves, where it rightfully belongs.
The introductory material in this blog helps document the party's connection to slavery. I would also like to point out the Lincoln-Douglas debates on slavery. They debated the topic from city to city in Illinois as they ran against each other for the US Senate seat from Illinois. The people of Illinois chose Stephen Douglas to represent them in the US Senate. Illinois is not part of the deep south last time I checked.
The topic of slavery is far more complex than what you get from the typical shame/blame America game that is volunteered by Democrats. However the Democratic party's role in slavery is simple. The Democratic party was a national party and Democrats, north, south, east and west supported slavery.
Slavery is but one of many topics where Democrats shift their shame away by blaming America. Further examples include segregation and systemic racism.