Liberia had colonial outposts of France, Spain and Britain but it wasn't profitable to expand in the area for them. The American Colonization Society (formed by a coalition of Quakers and slave-owners) began sending free people of colour to what would become Liberia in the 1820s as a way to limit potential slave-revolts in the response to the Haitian revolution and increased political activity among enslaved peoples in the US.

So yes, broadly under the protection of America who's businesses eventually paid off the other colonial powers to leave their outposts.

Interestingly, the Americo-Liberian settlers setup their own highly lucrative slave trade almost immediately after arriving in sufficient numbers.