Numbers are important to understanding the world, though of course there could be bias in any data set. It would be really worthwhile if you could identify a potential cause for bias in the data set. When data seems strange, it could be a sampling artifact (bias), or it could be real and up to us to uncover the reason for the strangeness...
I'll put my tin-foil speculations hat on for a second to offer a pro gun explanation for the data: what if higher rates of gun ownership led overall to fewer crimes overall because some sort of deterrence from gun owning population?
The point is, it could be bias, however the differences are quite large, suggesting that it's more likely to be incomplete understanding of the factors at play, warranting research studies to investigate why such differences in crime might exist between two quite similar countries.

Thanks for this point. I'm sure there are differences in the crime reporting methods between US and Canada, and frankly between each agency keeping and aggregating crime records from the lowest levels of policing orgs on up the hierarchy. It would take more time than I had to try and fully understand what difference there may be, though I would appreciate if you had a suggestion on a practical methodology to go about adjusting for biases in these sorts of comparisons.
The potential for bias in the gun violence data sets is why I chose to focus on comparisons between US and Canada, which share a lot of cultural norms, if that makes sense. All potential for bias aside, I think the data are at least interesting and informative, and most importantly to me, got some healthy debate going on several fronts.

Full discussion of the data can be found at https://pencer.substack.com/p/guns-in-the-usa-and-canada

Sources:

Crime rates in the US (2020- https://en.wikipedia.org/wiki/Crime_in_the_United_States ) and Canada (2017- https://en.wikipedia.org/wiki/Crime_in_Canada )

Gun-related fatalities in the US and Canada (2017/2018- https://en.wikipedia.org/wiki/List_of_countries_by_firearm-related_death_rate )

Civilian gun ownership (2017- https://en.wikipedia.org/wiki/Estimated_number_of_civilian_guns_per_capita_by_country )

50 US states gun ownership rates (2013- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4809774/ ) and gun fatality rates (2021- https://www.cdc.gov/nchs/pressroom/sosmap/firearm_mortality/firearm.htm )

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