I don't really have a dog in this fight. But as an American, who also has a son who plays competitive Soccer, that red card is precisely the reason why most people in the US think professional soccer players are just massive, massive, massive pussys.
Its bad enough that ever two minutes somebody is writhing in pain on the ground like they just got sniped from 200 yards away in the leg, but then miraculously recover to full sprint mode seconds later when they don't hear a whistle. It's definitely being a pussy, but we've become accustomed to that.
The only basis for a red card in that spot is "he MIGHT have hurt somebody". Didn't actually hurt them. Just "MIGHT" have. That's why soccer gets viewed so poorly domestically among large scale fans.
Best thing the coaches for my son's teams have done... if you're down writhing in pain for more than about 5 seconds, you're off the field. You get subbed out. Maybe you come back on, maybe you don't. So either you're actually hurt, and you need to come off, or you're exaggerating a boo boo in an attempt to goad the ref into calling something. And in youth sports, they call virtually nothing, which is refreshing.