The US participated in the Conference and signed the General Act, but the incoming Cleveland Administration (which took office a week later) didn't pursue ratification. A US taste for overseas empire was a decade away, and Democrats remained even then less enamoured of the idea. A revised convention was ratified by the US in 1892.

US aims centred around the issue of free trade, ensuring that signatories' goods could enter much of the continent duty-free. But US associate delegate Henry Sanford also acted as a cheerleader for King Leopold's ambitions in the Congo, with disastrous results for those consigned to his rule.

I'm far from an expert so I would recommend to take this comment with a grain of salt and wait for others to reply. However, I don't think USA was involved at all.

Despite being a large economy, at the time of the Conference of Berlin the USA were not an influential power in the classic sense of the term, as they were too far away to have a saying in European affairs. They weren't either a colonial power, as Cuba, the Philippines and Puerto Rico wouldn't be under American protection/rule until 1898, and it would only be after WW1 when the USA would step in the global community as a major superpower.