Criminals skew young and overwhelmingly male.[1]
>Do we have numbers that show a higher population of males in the US than in Canada over that time period?
It appears the baby boom was about the same size or slightly larger in Canada than the US.[2] As you can see from my first post, there also was an increase in crime in Canada during the same time period as in the US, but not as pronounced.
Unlike Corn, who is claiming that leaded gasoline is the primary cause of crime, such that it explains the entire or nearly the entire late 20th-century rise and fall in the US crime rate, I am making the much more conservative claim that the ratio of young men in a population is a cause of crime.
Indeed, as I said, the Baby Boom was not large enough for it to have been the primary cause of the US crime wave. (Although it might be sufficient to explain the relatively-smaller Canadian crime wave over the same period).
[1] https://i.imgur.com/2WscI1P.jpg — The chart understates the correlation between youth and crime, because prisoners might be serving multi-year sentences, they may have got away with other crimes prior to those they're serving time for, and first-time offenders are more likely to receive a shorter or no prison sentence than recidivists are.