The American Colonization was never formally a part of the US government, no. However, at the height of the organization's popularity it did enjoy support from Congress. There were six major centers for settlement along the coastline set up by the ACS and a seventh was established by the government itself in the 1820s. The colony set up by the US government was eventually incorporated into the rest of Liberia after interest waned.
Wikipedia does refer to a seventh colony established by the US government, but I'm not so sure that's accurate. I'm fairly familiar with the colonization society archives of the time, and I've never seen any reference to a federal colony. I
think the Wikipedia article is referring to New Georgia, which is the place where the US Navy deposited slaves who they confiscated from captured slave ships. If so, then it wasn't really a Federal colony, because the government didn't supervise or support it.
I thought of this too but wasn't really sure how to word it. This sort of puts Liberia in legal limbo where it is de facto independent. I'm not sure how this would impact the cultural identity of the colonists and its foreign relations though.
It might introduce a narrative of betrayal into their relationship with the United States, which would complicate their belief in America as their motherland and might even cause them to look elsewhere for a patron.
If I were a part of Congress during this though, I would just offer Liberia the option of being a Freely Associated State/ Protectorate. It gets rid of the various diplomatic and legal headaches while improving the prestige of the US on the national stage.
One option would be for the Federal government to just assume responsibility under the "commonwealth"
constitution of 1839, which essentially did make Liberia a free associated state. This constitution called for an appointed governor, an elected lieutenant governor and an elected legislature, and the government could take over the ACS' role of appointing the governor and its veto power over legislation. My guess is that it would revert to appointing white governors, though, which might cause the Liberians to give independence a second look.