While I agree with Fairmount about Lasix/dehydration leading to fewer starts, one would also think that the associated weight loss would - if anything - reduce the stress of racing, not increase it.
Would also agree with your points re Europe (slow early / fast late) vs US (the opposite, turf excepted). That was probably the biggest reason why many bettors hated synth - it seemed to turn speed from an advantage to neutral/disadvantage.
I see many trainers note the "urban" distinction. Not sure how much of a factor that is, but since Euro horses don't live at racetracks, they generally get to "be horses" more than their American counterparts. I'll add that one of the recent big name converts to the WHOA group (Motion) operates mostly out of a Euro-style yard.
Here's another good read from today that touches on your point about the economics for owners.