Residential US electricity primarily uses center-tapped single phase transformers, with 240V between the two ends of the coil, and 120V from either end to the m

Residential US electricity primarily uses center-tapped single phase transformers, with 240V between the two ends of the coil, and 120V from either end to the middle. The center tap is grounded and treated as a neutral for 120V loads from either "hot", and 240V loads run between the two "hots". The advantage is that we get 240V power with 120V shocks (assuming you grab a hot wire while you are grounded). The disadvantage is exactly what the original post was about: if the neutral wire breaks, it can fry everything in your house, because your toaster is now in series with your lightbulbs between the hots.