This isn't correct for most residential installations in the U.S. for most of those, they have split phase power (https://en.wikipedia.org/wiki/Split-phase_elec

This isn't correct for most residential installations in the U.S. for most of those, they have split phase power (https://en.wikipedia.org/wiki/Split-phase_electric_power https://en.wikipedia.org/wiki/Split-phase_electric_power) provided by a center tap transformer. This produces a neutral and two hot wires, each 180 deg out of phase from each other. Hook either hot to a neutral, and you get 120V, hook one hot to another and you get 240V. In some places though, (I know it's common in New York, and also in a lot of datacenters), they do something like you describe, and hook 2 phases of a 3 phase system together. Since these are only 120 deg out of phase from each other instead of 180 in the split-phase system, you get less voltage, specifically 208V.