The US was not "one of the first" to abolish slavery by any sensible definition of "one of the first"; it was in fact one of the last western nations to abolish slavery.

It is true, of course, that some countries continued to profit from the slave trade while abolishing it within their own borders (the UK being an example). But there were others that didn't, or at least not to any notable extent, and some had abolished slavery centuries before the US.

For clarity, this is not a criticism of modern America or modern Americans. It's just an observation that the US cannot claim to be a pioneer in abolishing slavery.