

Chicken and egg situation, Americans drive because that’s how their cities and suburbs are laid out (excluding NYC, for the most part).
They don’t rely on alternatives because they are slow, inconvenient or non-existent; alternatives can’t be built up as the costs can’t be justified based on existing patronage levels.
It’s not so much about being built on a grid, but rather being built with a particularly high population density in mind - and further supported by a robust public transit network.