This is a good review. As much as I loved Caplan's book, it's good to point out its less compelling points.
I just feel like commenting one line in the opening part of the post.
Immigrants commit more crimes than native-born Europeans but fewer crimes than native-born Americans.
Yes, that is somewhat true. But I have looked into this claim for Italy (where I've spent most of my life), and it turns out it is only true before adjusting for age. Foreign-born commit more crimes because they're younger on average. When you compare homogeneous age groups (say 18-to-25-year-olds to 18-to-25-year-olds of the other group), it looks like the crime rate is virtually the same. I wouldn't be surprised to find out this to be true of several other European countries. Also, crime rates are particularly high for illegal immigrants, but I wouldn't know how much people self-select themselves into legal and illegal immigrants, so where the causality is. But the above descriptive statistic (same crime rate when accounting for age) could be a useful argument - in Europe - in favour of the case Caplan is arguing for in the US.