In Canada, convictions for perjury are almost unheard of but America
manages to convict people of perjury.

In America, a girl rapper recently got pinched for lying to a Grand
Jury in the USA.  In Canada a Superior Court judge, acting in the role
of Commissioner presiding over a quasi-judicial public inquiry made
Findings that many witnesses lied under oath.  A newspaper columnist
opined that these witnesses still have little to fear.

In both countries criminal convictions require proof beyond a reasonable doubt.
So, how to explain the difference in perjury convictions? 

At the respective federal levels, compare Canadian criminal perjury
offence up against the American U.S.C. criminal perjury offence.
  
Is it different levels of prosecutorial zeal or is it the wording of
the respective charges and proving all the essential elements or
something else?