Bridget Huddlestone, from New Zealand Young Farmers, who is accompanying the group, said it would be an "amazing opportunity".
Sarah Humphries (17), a pupil at Southland Girls' High School, was both excited and "a bit shocked" about her selection.
Her parents operate a 570ha farm at Five Rivers which runs sheep and grazes dairy heifers.
"The United States has large ranches and feedlots and I can't wait to learn more about their style of farming," she said.
It was hoped the inaugural exchange would become a biennial event. Sarah and Tyla have both completed the Leadership Pathway Programme, a leadership course run by New Zealand Young Farmers and funded by the Red Meat Profit Partnership.
It had been developed to identify emerging leaders and ensure they were entering career pathways in the primary industries.