Hi Mads,
I added the following code to show data for any state using Manipulate.
cases[state_] := 
  ResourceData["Epidemic Data for Novel Coronavirus COVID-19", "USCounties"][
    Select[#State == state &], {#County, #ConfirmedCases["LastValue"]} &] // Normal;
Manipulate[
  GeoRegionValuePlot[Rule @@@ cases[state], 
  GeoLabels -> (Tooltip[#1, Column[{First@CanonicalName@#2, #4}]] &), 
  ColorFunction -> cfunc,
  ColorFunctionScaling -> False, 
  PlotLegends -> legend, 
  PlotLabel -> "COVID19 cases in " <> First@CanonicalName@state, 
  ImageSize -> Large], 
 {state, EntityClass["AdministrativeDivision", "USStatesAllStates"] // EntityList,
   ControlType -> PopupMenu}]