Some of the Giant Canada Geese get pretty light in the body. Certainly not white but could look that way if the sun is hitting them just right. Combine that with the white underside and that could be what you saw.
Of course you have the possibility of a crossbreed or a mutation of some sort. I don't think a true albino goose would have the black neck/head and black bill.
Where are the pics of this thing?
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