Advanced KML Overlay

I have posts which are U.S. Counties.

Using the Google Maps and my custom Lat/Long fields, I can show auto-associate a map to each post. Cool!

However, Google seems to have County boundaries in KML, discussed here:

I would LOVE to be able to assign kml as a custom field(?) or similar to each of my posts and have the appropriate KML overlay the map, which is centered at the lat/long of the county centroid.

I am open to ideas, suggestions, etc. Thanks!