Your correct for the most part Bub
Most do have 220vac coming into the main box
2 legs of 110 and a Neutral with the main box having a ground installed.
Ive worked on some larger homes that had 3 Phase coming in but they were also powering shops on the same property as well.
Someone correct if Im off but the purpose of the 208/220 is to balance the load across the circuits when powering larger appliances such as A/C, elect stove, water heaters, Air Handlers w/ heat strips, etc...
I believe outside of that the only difference between us and Europe is the Cycles, 60 v 50 overseas OHHH and the oulets are different