I don't know about length of grass blades, but it might have something to do with the firmness of the ground. I'm guessing but I would think the firmer and faster courses would favor speed horses and softer ground would probably favor stayers more. Then there's a course labeled "good" which I think is slower than a course label "firm" (I hope I'm getting my facts straight, otherwise I'm going to feel a little foolish - LOL).
I have a strong hunch in Europe the turf courses are probably softer than over here, thus favoring more stamina horses. However, Sea The Stars, prefers firmer courses and if the course is too soft, Oxx doesn't like to run him. Relatively speaking though, I would suspect a firm course across the Pond is probably still softer than a firm course over here, but I obviously have absolutely no way of knowing, except for the fact that Americans are more speed focused. Europeans of course run virtually all their races on grass and the courses appear to be a lot wider. Many of the races also are run on courses quite challenging because they're irregular, that is, they slope, become a little "hilly" and are not always level ovals. Do they also run some of their shorter races on a complete straight? Events are contested clock-wise, although I'm not sure if they run all their races in this direction.
Weather of course would also influence the condition of a track and how fast it dries out. The Monmouth course during the '07 Breeders' Cup was like a bog, and outstanding turf specialists who thrive on firmer ground had a terrible time over it.