Do what you want as its your money.  My point of supporting the American economy is that by shopping in the US, you are giving jobs to Americans rather than Canadians - from sales associates, to distributors, to truckers, etc.  And jobs fuel the economy.  Every product bought in a country feeds that country's economy.  It's basic economics. 

Feel free to shop where you want.  It's a free country.  Personally, I don't like cross-border shopping for more reasons than just the warranty issue.  There are fundamental issues with it.  But that's my opinion. 

Ultimately, if you want to take issue with the pricing of electronics in Canada, you should be contacting the manufacturers and complaining to them.  They are still the ones dictating the prices to companies like Future Shop.

(Note:  I do not work for Future Shop, nor have I ever.  My opinions are my own and my own only).