There were far more slaves taken to the Caribbean where the Brits had their sugar plantations and made the most money of any of the colonies in the western Hemisphere. Weren’t many Americans in places like Jamaica where slaveholding was widespread.
The Brits outlawed slavery, the US didn’t for another fifty years or so, look I am not defending the Brits but Americans criticising the British for their role in slavery? Let’s just say it’s not the best line of argument to take if the moral high ground is your key position.