I find it extremely disingenuous to say that because the Canadian (or British)
Constitution can easily be re-interpreted in different contexts, that it will
always be interpreted in 'the correct way.' You seem to be pointing to examples
of the US Constitution being interpreted poorly, making the implication that a
'dead tree' constitution can
only be interpreted poorly, and a 'living tree'
constitution can
only be interpreted in a good way.
A constitution that can be easily re-interpreted may allow for your government
to 'turn on a dime,' but it makes no claims to whether your government is
turning in a good or bad direction.
As to the US Constitution:
* The US Constitution can be re-interpreted by the US Supreme Court through the
setting of legal precedent.
* The US Constitution can be amended by Congress. (Prohibition was a
Constitutional Amendment).
* The current interpretation of the commerce clause could be overturned by the
US Supreme Court should a case come before them, and the make-up of the
justices leans towards overturning the current state of affairs.