Final answer:
Joel Roberts Poinsett, an amateur botanist and the first U.S. Minister to Mexico, introduced the poinsettia to the United States in the 1820s. This plant is now commonly associated with Christmas celebrations in the U.S.
Step-by-step explanation:
The individual responsible for bringing the poinsettia to the United States was Joel Roberts Poinsett.
He was an amateur botanist and the first U.S. Minister to Mexico. In the 1820s, while visiting Mexico, Poinsett became enchanted with the brilliant red plants he saw there. He began sending samples of the plant, which was known locally as "Flor de la Nochebuena", or "Christmas Eve flower", back to his greenhouse in South Carolina.
Through his efforts, the plant came to bear his name and is now associated with Christmas celebrations in the U.S. His job, aside from being a diplomat, included a variety of roles in government and working with nature.