Americans DO take their shoes off when entering their friends' house. At least those in Ohio do. That is where I lived for six years. May be different in other parts of the United States.
That is not my experience, Yukon. I lived in USA for seven years, but I rarely saw anybody removing their shoes at the door. I don’t know why this difference between USA and Canada.
SirJoe, You lived in Utah, and that's where my Daughter-in-Law also
comes from. People removing their shoes in a private residence was
one of the many things she found "weird" when she first moved up to
Canada. That and the prices that we pay for food (Meat, Cheese,etc..),
and people on the street that she'd pass would say "Hello!!" just 'cuz
they where on the same sidewalk, and all the not-very-new cars that
are still on the roads on the Prairies.
Not removing ones shoes in a private residence might be a regional
thing in the USA, but my Daughter-in-Law confirms your experience
as far as Utah goes.