This is also the case in Europe just with different numbers. There are three 230V legs, each within 120 degrees of phase difference from each other. If two are combined, you get 230V * (sin 60) * 2 = 400V which can be used for industrial applications.
Not quite - the US has a unique split neutral where an incoming 240V single phase is divided into +/- 120V to drive either 120V to earth or 240V heavy duty appliances. But the dryer supply in the US isn't a multi phase
That is the single phase that is common in most residential service in the US. It is separate from the 3 phase service you find in light industrial and large office buildings.
