Spinal cord injuries often occur when people are in severe car accidents or when young men or women are playing in a high contact sport. The problem with spinal cord injuries is that you don't want to move the person because you might actually cause further damage that hinders their ability to enjoy the rest of their life. That said, it's important for you to respond as a witness in case you see a spinal cord injury happen. Just because the injury didn't happen to you doesn't mean that you shouldn't show concern and respect for the other human being.
Many Americans don't like the idea of slip and fall accidents, because you can technically fake a slip and fall accident and then waste taxpayer money by bringing it to court. You also might slip and fall and a lot of people consider this your own fault. Obviously, this is an extreme view and slipping and falling is no laughing matter. You need to be aware of your surroundings and understand that the American justice system is an around to cater to your clumsiness, but homeowners in building owners have a responsibility to keep their floors and outdoor areas safe so that people don't get severely injured. If you walk into a restaurant and the entire floor is covered in grease then you can't expect anyone to not fall.