KML layers disappear on small zoom level

I've got a problem with KML Lay开发者_如何学Goers. All the layers that are plotted on the map look good on initial zoom level. If you change zoom level to lower one you'll see that some borders and white areas dissapear. If you magnify the map to the initial zoom level again - it works. Strange.

Could you take a look? Here is the example for USA: http://tinyurl.com/kmlproplem. On zoom level 3 (default one) you will see the two parts of USA filled with white color. On lower zoom level only one part of it is visible + some borders dissapear.

Thanks!

Ok. I've resolved the issue. The problem was too detailed KMLs. I used simplified version for small zoom levels and more detailed one for greater zoom levels.