The Americans' aren't immune to messing things up, but they do it a lot less than the Brits. Practice is what we need. Practice and experience of running competitive relays.
Part of the issue is the not practicing of relays.
The Americans athletes grow up doing relays for their respective College teams - they know the event inside out. You cannot get to the top in US sprinting without running more than a few relays. They know how to do a changeover and...