Big difference between odor detectors, which they use in every airport, and an x-ray machine that would look into your house. You really need to read up on the 4th amendment, before you start talking about big brother coming to get you.
The difference between the enhanced information gathering techniques of a dog and the enhanced information gathering techniques of an x-ray machine are arbitrary.
You implied that the delta between the officer's nose and the dog's is insignificant. But if that delta is insignificant then the delta between the dog and a chemical detection systems must also be insignificant. Likewise the delta between any other of the officer's senses like sight and an enhanced mechanized version like x-ray must also be insignificant.
If this is not the case then the reason is arbitrary. i.e. x-rays are not to be allowed on Tuesdays between 4.15am and 6:34am on brown station wagons in March during leap years. In other words you are arbitrarily finding one Ok and the other not to suit the basis of your argument. It might be nice to think that there is some kind of magical line that separates the two but absolutely nothing in what you wrote proves that.