Lott has been debunked a few times. Here's a recent article
with a summary explaining the flaws in his reports:
Regarding the Cato Institute's examples of Israel and Switzerland: seems like cherry picking two small, mostly homogenous societies. What about places that are more comparable to the US like Germany or France?
And for your final example: how many guns per person do those seven European countries have and how does that number compare to the US? Our country is flooded with guns. Just about enough for every man, woman, and child.
Anyway, I don't think gun control will ever be implemented in the US in a way to produce any meaningful results. That ship sailed over two hundred years ago. We might as well just get used to the idea of mass shootings occurring on a regular basis with ever increasing body counts.