Many reasons...
1)The kit will not fit the US Spec car
2)No provisions on the kit for US emissions
3)Mainly, the blower is not an Eaton M90, it is a Yella Terra YT1500 housing with properly liscensed Eaton M90 internals. Yella Terra has implicit instructions not to distribute their blowers to the US, as this is a part of their agreement with Eaton. Only Magnusson Superchargers can distribute Eaton blowers within the US to the Consumer market.
4)No local support of any kind
Don't be upset with Neal, he can't sell one to you even if he wanted to. I heard rumors that he has a project that will work in the US, but I have no idea if there is any validity to it.
If you are a DIYer, ask him if he can sell you the manifold plate. If so, you can make an adaptor and build your own SC kit for your car...
Ryan