Ed, I moved your question to the Forum as the original location you posted is meant for questions directly related to the forums itself, not Tableau products. Don't worry, it is confusing at first so no harm
I checked a map on my company's Tableau Server and it rendered quickly so I don't think this is an issue with the Tableau mapping service. I'm not a Desktop person so I won't be able to help here but to help others, are you using a shape file or custom polygons? The delay may be due to the complex underpinnings of your specific worksheet.
This also loads up and responds quickly to me using the Tableau Public link (I tried some selections, panning/zooming, etc.). I also downloaded the workbook and don't see any issues to point out why it would be slower when you load it. Since you're using the Tableau custom geocoding there shouldn't be any major complexity in the data slowing things down.