I can understand if you were importing a proven titled German dog with all health clearances for breeding purposes but a puppy??? Not only will you be paying for the puppy, you will also be paying to have the puppy imported to the US, you will also be putting the puppy into quarantine for a period of time, which in my opinion is not good for a puppy. This is the time for a puppy to be socialized and loved, not to be put in a cage with no interaction with you.
Your German rottweiler will have a tail. The standards for Rotty's in Germany, Canada, USA, Australia, UK etc are all the same, so I am unsure as to what other differences your wife can spot....
You've stated you dont want to show the puppy, why are you going to such an expense for a dog you say will be pet quality only? Can you not buy a puppy in the US or Canada (with a tail because that's the only difference you will see) for less money and put the rest of the money in an account for emergency's. Better still, there are thousands of abandoned rottweilers all over the US and Canada who would so love to have a home to call their own with someone who will love them and teach them.
If you are still set on getting a dog with German bloodlines, then get a puppy from the US where both parents were imported from Germany, you will save yourself time and money....BUT remember, just because a dog was born in Germany or has German bloodlines doesn't mean that the puppy will be healthy - you never really know what can happen. Just make sure both dog and bitch were heath certified and OFA registered.
Just my 2 cents worth....which is nearly worth 2 cents in the US now!!