What facts help to explain how Americans became the way they

They left their own world for the unknown world. So they were risk-takers.
Because they had a hard life living on the front life, they were tough and self-reliant.
Frontier men and women often faced new problems and situations. So they learned to experiment with new inventions and new ways of doing things.
Because they had willingness to experiment, they got a sense of optimism that every problem had a solution.
They had to overcome many difficulties, and thus they had to cooperate. So they became capable for volunteer actions.
Because they had many difficulties they became very hospitable.
Because they moved from east to west acquiring new territories, they are always on the move.