Why has American work ethic been seen as a key ingredient top our economic success?

Convinced that selfreliance, the work ethic, and aggressive individualism forged in the crucible of America's frontier experience had been key ingredients in the ... what would sustain such traits in a 20th-century world marked by the growth of ... industrial labor, their presence was essential to the country's rapid economic .

Explanation:

the monroe doctrine is the best known u.s. policy toward the western hemisphere. buried in a routine annual message delivered to congress by president james monroe in december 1823, the doctrine warns european nations that the united states would not tolerate further colonization or puppet monarchs.