Perhaps the most successful attempt at convergence so far has been the Europlug, but only because it’s a weird compromise. Did you know the europlug prongs aren’t actually parallel? They angle inwards slightly and have a little flex, so they can be accepted in multiple European countries’ sockets that actually have slightly different dimensions! It’s a cool design, but you wouldn’t intentionally design it that way if you had the opportunity to standardise the world from scratch.