I am not sure what you are doing, but to create the annotatate dark state lines, all you need is maps.counties.
One possibility is that you are doing something to change the ordering of state and county borders. Then when your annotate code traces the state lines, it is tracing some county lines instead of state lines.
Another possibility is that you are removing counties and leaving holes in the state. These "county" areas that are outlined in black are bigger than a county in my map. For example, in Texas there is a large place up near Oklahoma. But on my map there are many smaller counties in the same area. If there is a hole, like a lake, Annotate surrounds it by dark lines. Is it possible that you are removing counties and leaving holes that then get surrounded by dark lines? I notice that these holes/counties are white.
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