What does population density mean? Number of people per household square footage? Number of people per household? Number of people per zipcode? City/rural? Population density is not a consistent predictor of covid19 spread by any of these measures, unless you also start taking other factors into account. Density matters "intuitively", but it's not borne out by the data.
The rise differential now is the first good example of measurement of policy effects.
These are not political points, just data points.