My understanding is that if you had the newest *C dish with the quad LNB (a small box with 4 connectors on it) in Canada, there is no direct substitute dish that can be used because that style LNB is proprietary to *C and can't be purchased elsewhere.
If you had the older style dish in Canada, the one with the LNB that looks like two tin cans, then you could substitute two generic FTA dishes (e.g. Patriot 85's) to capture the two *C satellites. If you were interested in English-only and no HD, you could use just one generic dish and point it at Anik F1R.
In truth, even if you had the newest style dish in Canada, you could use the generic dish setup in the US, but you would need to call *C and request they make a change to the software in your receiver, which they would send to you remotely via the satellite. However, such a call might result in the CSR inquiring as to why you didn't sign up for the "home away from home" package, in which case *C would have provided you with another standard *C dish in exchange for $50. I don't think they would send the dish to a non-Canadian address, though. Additonally, you would then need to reverse the change process when you returned to your home.
There's more information about using generic dishes for *C on the Global Communications website under the "Canadian Solution" page. You may need to dig a little to find the right sub-page, or you can call them or e-mail them. They're very helpful.
