Canada, a bit more liberal than the US, probably has plenty of cities with such policies in place too. Yet, no crime wave there. These waves were a result of Kia's choices, and quite obviously so.
On the contrary, Canada's rate of stolen cars is only 10% less than the US despite having very few port cities. <https://www.bbc.com/news/articles/cy79dq2n093o>
If it did, that would point to a US and Canada crime trend correlation. If not, then you can't just say that the one static variable, city/county level policy and the independent variable, immobilizers, are the only factors.
You have different criminal populations, societal values, amounts of government aid, rehabilitation programs, etc that all play into the analysis.