I'm not a dealer, so all I have to offer is "conjecture". I think part of it has to do with the Canikon dominance in the SLR market here. We typically have no problems getting Panasonic Point and Shoot cameras. I also think it has to do with the Big Box stores wanting to discount everything, which reduces Panasonic's margin potential. This means either the big box stores are unwilling to stock them or Pansonic is unwilling to sell at the price the big box stores want.
Some of it may have to do with the Yen to US dollar and Euro to Yen.
The G3 retails on Panasonic's website for 699 USD, which is 57315 Yen.
The G3 retails in Germany for 699 euros, which is 81783 Yen.
So, it benifits Panasonic to provide product to Europe over the United States.