yeah I also saw it twice in Germany in March 2016. very very full/sold out Shows. Europe never is a crowd wise for them. The 2nd leg in the USA however seemed to more of problem.
Europe's crowds are generally much larger than those in North America, absolutely. But I remember hearing from some (who live there) that even in Europe, the crowds are shrinking. When they did a second run through Europe in 2014, this was more evident. I would imagine if they would have done the same thing again (doing a second run through Europe, playing many of the same areas with the same TA setlist), the turn out would not be as good either. Shifting gears and revamping the setlist to focus on IaW and ACoS, as well as changing things up live with the jams and improvs definitely made a difference in fan interest.
As for comparing the first and second North American legs, I think one thing that is often overlooked is the fact that the dates were announced before the album went on sale, and therefore before anyone heard it. Being as polarizing as it has been, a lot of fans love it, but a lot of fans have been turned off by it too, and probably wouldn't have bought tickets had they known what the album would be like, which is what happened to one of my friends.
Two other things that I don't think helped the second run through North America (besides the fact that they were only doing the new album, and not playing anything from their previous albums) are that some of the shows were booked very closely together, or at least in close proximity to where they played on the first leg of the tour. While some fans may argue that it was worth seeing multiple times, without having changes in the setlist from night to night (as in days of old) and higher ticket prices didn't motivate many fans to see show more than once (as was the case with me). And having the dates dribbled out, causing some fans to purchase tickets to shows some distance away, only to find out closer shows were announced later didn't help either.