'COVID Knows No Boundaries' - Michigan Excepted?

A nonprofit called the National Democratic Institute states, “#COVID19 knows no boundaries.”

Michigan Gov. Gretchen Whitmer said in April of 2020: "This virus moves easily from person to person, especially in the areas with higher density. COVID-19 does not contain itself to city limit, to county line or to state line."

If true, Michigan appears to be an exception.

The New York Times tracks COVID cases by county in the United States.

The map of Michigan shows that the spread of COVID appears to stop right at the state border.