As a matter of fact, the United States did experiment with African Colonization. After the American Revolution, many Whites and Freed Blacks weren't sure, or did not believe race relations in the United States would improve. As early as 1792 (this date keeps getting pushed back, interestingly enough) Free Blacks were petitioning for emigration to other lands, the most notable petition comes from fifty five notable Black Philadelphians including Richard Allen, father of the Black Church, it reads:

We have with other men an Inalienable Right to life Liberty & the pursuit of happiness, so that nothing may be wanting on your part to facilitate so desirable an object of opening a door for gradual Emancipation to take place, and likewise to look forward preparing an asylum… similar to the one prepared by the British in Sierra Leone.

Born out of uncertainty, a desire to improve race relations, and inspired by the British Colony of Sierra Leone, home to many former British and American slaves. There began a push for the creation of an African colony, run by Free Blacks and sponsored by White philanthropists. The largest sponsor of these groups was the American Colonization Society, founded in 1816. From these "Colonization Societies" sprang small colonies such as "Mississippi-in-Africa" and the "Republic of Maryland" on the West African Pepper Coast, though both would be annexed into the greater state of Liberia, founded in 1822.

Men from a variety of backgrounds, black and white, Northern and Southern, supported this movement, white Reverends such as Ezra Stiles, Samuel Hopkins and Robert Finley, Senators like Henry Clay and successful Black businessmen Paul Cuffee and James Forten all got behind the movement. While Colonization schemes such as the ACS (discussed below) had heavy support from many northern white communities and some black ones. Colonization schemes were attacked by many African Americans as racist and counterproductive to black desires, and by southern planters as an "abolitionist plot" to end slavery. One of the most powerful groups involved, founded in 1816, was the The Society for the Colonization of Free People of Color of America or the American Colonization Society The ACS was the group to spearhead American Colonization Schemes and led to the founding of Liberia in 1820-22, which became the colony where more than 12,000 newly freed slaves would travel and colonize. It lost funding and support quite quickly and sputtered along for several years after its heyday.

Though for some time the ACS seemed beaten, the death of Paul Cuffee in 1817 and the racist stance of the Colonization Society’s membership alienated free blacks from any kind of African emigration. A new outlet for free blacks looking for escape became necessary, and this outlet came in the form of Prince Saunders and the Republic of Haiti. Published in 1818, Saunders’ Memoir Presented to the American Convention for Promoting the Abolition of the Slavery and Improving the Condition opened up Haiti as an option for safe emigration. This memoir portrayed the island as “luxuriant” and “beautiful,” and utilized the fact that “the authorities of Hayti are themselves desirous of receiving emigrants from this country,” as a method of appealing to the pro-emigration populace. Saunders, under the employ of Haitian President Jean-Pierre Boyer, was to convince as many emigrants as possible to settle on the island. In one letter to a supporter of emigration, Boyer wrote, “I have thought that a finer occasion could not have presented itself to offer an agreeable hospitality, a sure asylum, to the unfortunate men, who have the alternative of going to the barbarous shores of Africa, where misery or certain death may await them.”

Boyer saw American emigrants as industrious and hardworking in a time when the island's economy was failing, in addition to the fact that he lacked manpower to both work the land and fight in his armies should France attempt to invade again. Letters from abolitionist Richard Peter, Jr., to the Emperor of Russia give evidence that white abolitionists supported Haitian emigration as well, for Peter attempted to convince the Emperor to acquire Haiti as a “means of ameliorating the condition of the free people of color.” To these abolitionists, and the Haitian population, fear of French reinvasion seemed a constant looming threat; therefore, if another European power stepped in and controlled the island, it would prevent France from re-invading and persecuting those freed African-Americans who had emigrated there.

The push for Haitian emigration continued well into the 1820s with the establishment of emigration societies in cities across the North, such as New York, Boston, and Philadelphia. Unlike Liberia and the ACS, Haitian emigration received enthusiastic support across the board from black leaders. Richard Allen served as President of the Philadelphia Branch, while his son served as secretary, with the junior Allen later moving to Haiti for a short time. The Board of Managers list also serves as a who’s who of African-American leadership. Richard Allen, James Forten, Joseph Cassey, and James Prosser all held prominent positions in the Philadelphia Branch of the Haitian Emigration Society.

As early as 1825, however, reports began filtering back about the actual conditions on the island, similar to the first wave of emigrants to Liberia. Initially, the leadership class promoting the scheme wrote, “and satisfaction with their reception in Hayti. We regret that reports of a different character are flying about, as we know not of the least foundation for them, and believe them all false. We would remind our brethren, that as we have long been the victims of oppression and injury, of selfishness in its worst character, we ought to put little confidence in evil reports, which are circulated by persons inimical to our welfare.”

Governmental harshness, religious intolerance, the threat of war, and a host of cultural differences separated the Haitians from their American counterparts. Though some of the American emigrants stayed, many returned to the United States to tough out a living under its oppressive laws. One longtime resident of the island later stated, “Of all Boyers thirteen thousand American immigrants of 1824-1827, I never found nor hear of one who, after 1836 was living on the land assigned him by the government on his arrival. A considerable number of these immigrants, and probably some of the best of them… returned to the United States.”

After the failure of the Haitian Emigration Scheme, many looked back to Liberia, despite the many issues. It was overly expensive to ship people and their families across the Atlantic, and many Colonization Societies simply couldn't afford it. Also an issue was that since its inception, the ACS and other schemes were under constant barrage by large portions of the black community, they couldn't get funding or public support and sort of went away. The great rejoicing of the end of slavery turned many Pro-Emigrationists, such as Martin Delaney, who spent much of his life preaching the Emigration cause but during the Civil War joined the Union as a Major and led a Regiment of Black Troops. Unfortunately, much of this hope would be crushed by the failures of Reconstruction and leading to a second wave of emigrants. Several hundred left out of Georgia in 1868 and South Carolina in the 1870's as well a pronounced trickling of emigrants throughout the years. Most of these men and women were recently freed slaves.

The United States very much treated Liberia as a protectorate, and protected her against foreign encroachment though never officially recognizing it as American Territory. In 1843, Secretary of State Abel Upshur wrote a terse letter to the British Diplomat after they had made moves to annex a section of northern Liberia.

this Government regards it [Liberia] as occupying a peculiar position, and as possessing peculiar claims to the friendly consideration of all christian powers; that this Government will be, at all times, prepared to interpose its good offices to prevent any encroachment by the colony upon any just right of any nation ; and that it would be very unwilling to see it despoiled of its territory rightfully acquired, or improperly restrained in the exercise of its necessary rights and powers as an independent settlement.

Out of this grew a larger problem, the US wouldn't officially recognize or annex them and wouldn't allow other powers to either. So in 1847, Liberia declared its independence and wrote the 1847 Liberian Constitution a document full of references to their own past, showing their still strong connection to the United States:

We the people of the Republic of Liberia were originally the inhabitants of the United States of North America.

The United Kingdom recognized Liberia the following year, though the United States would refuse to do so until 1862 when President Lincoln recognized and sent diplomats to Liberia and Haiti (the two Black Republics).

Sources:

• Richard Newman, Freedom's Prophet: Bishop Richard Allen, the AME Church and the Black Founding Fathers

• James Sidbury, Becoming African in America: Race and Nation in the Early Black Atlantic

• Julie Winch, A Gentleman of Color: The Life of James Forten