You can alter the boundaries and names using the Map > Map Options menu.
It might sound odd, but we found that if we added a data layer to the viz then the place names darkened. Works well for us over here in Australia since we don't need to zoom in on USA. Hopefully you'll find something that works
Step 1 - no data layer
Step 2 - data layer
Un check the country name in map layers and drag country name into label and increase size and color.