Members of Clan Hay immigrated to America and made significant contributions to the development of the nation. They played key roles as military leaders during the Revolutionary War and were instrumental in the westward expansion. Today, descendants of Clan Hay continue to play important roles in American society.

In Virginia, the town of Hayes was named in honor of Lt. Hugh Hayes.

In the United States, the surname Hay appears in various forms, such as Hays and Hayes. These variations originated from phonetic spelling conventions and the challenges of literacy during the immigration and settlement periods.

After the Revolutionary War, descendants of Clan Hay primarily moved south, settling in Tennessee. This lineage includes several prominent figures involved in political and military spheres, such as Governor William Hall, President Andrew Jackson (who married Rachel Donelson; her sister Jane Donelson married Col. Robert Hays), President James K. Polk (whose sister married Dr. John B. Hayes), and John "Coffee" Hays (from Wilson County), who led the Texas Rangers and was credited with first using the Colt revolver in battle, aiding in westward expansion.

After marrying Rachel Donelson, Andrew Jackson became connected to the Hays family through marriage. On July 5, 1804, he purchased a 425-acre farm from his neighbor Nathaniel Hays. Jackson subsequently expanded the Hermitage into a plantation, focusing on cotton production as a profitable enterprise.  As a result, the original Hays Station ceased to exist as a separate entity.

President Jackson named his property The Hermitage in honor of his brother-in-law and friend, John Hermitage Hays, which also gave rise to the name of Hermitage, Tennessee.

Donelson, Tennessee, is named after the Donelson family.

Numerous locations across the country are named in honor of the Hays/Hayes family. Haysborough (established in 1784, also known as Haysboro) and Hays Station (established in 1781, now part of present-day Nashville) are two examples. Hays Station was founded by Nathaniel Hays and Samuel Hays.

Haysboro was established by Col. Robert Hays in 1786, who married Jane Donelson, the sister of Rachel Donelson, Andrew Jackson's wife. Samuel Jackson Hays, born to Robert and Jane in 1804, was killed by Native Americans in 1793 near Hays Station, approximately 100 paces from the Donelson residence.

The city of Hays and Fort Hays were named after Major General Alexander Hays, a Union general killed at the Battle of the Wilderness during the Civil War. The original Fort Hays, located south of Victoria, was relocated in June 1867 following a flood. Hays City was established on November 23, 1867.

John Coffee Hays, born at Little Cedar Lick, Wilson County, Tennessee, was named after his relative by marriage, Colonel John Coffee. In 1836, at the age of 19, he moved to the Republic of Texas. Appointed to a company of Texas Rangers by Sam Houston—whom he knew from Tennessee—Hays received a letter of recommendation from his great-uncle, President Andrew Jackson. Rachel Jackson was Hays' great-aunt through the Donelson family.

Hays led the Rangers in campaigns against the Comanche in Texas and played a crucial role in the Battle of Plum Creek in 1840, alongside Tonkawa Chief Placido and his scouts. He also commanded forces during the Mexican–American War (1846–1848), supporting President James K. Polk’s westward expansion agenda. John Coffee Hays was also related to Polk through marriage. Hays County, Texas, is named in honor of John Coffee Hays for his leadership in the Texas Rangers and his contributions during the Mexican-American War.

The Hays/Hayes family has a long history of significant land ownership worldwide. This tradition continues today with Jeremy Hugh Gwynne Hayes, grandson of Hugh Gwynne Hayes and Gladys Anita Bain. Jeremy H. G. Hayes is recognized as one of the largest remaining landowners in Wilson County, Tennessee. He is the twenty-second great-grandson in the direct line of William de Hay of Leys.

Other Tennessee families that have intermarried with the Hays/Hayes family include the Pennington, Lane, Smartt, Jackson, Hall, Thompson, Wright, Donelson, Polk, Cage, Ligon, Belcher, and Eakes.