Earlier Guano Islands Act

The Guano Islands Act allowed private citizens of the US to claim uninhabited islands if they were not claimed by another country. The act passed in 1856 for the primary purpose of supplying guano, bird poop which was used as fertilizer. This act is the reason the US owns some minor islands/atolls in the Pacific and the Caribbean.

What happens if a similar act is passed in the 1820s? Perhaps the reason is for the whaling industry which operated from New England would love some little island bases. What other islands could the USA claim with a 30 year head start to OTL that are unclaimed but not important to others?
 
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