In all technicality, didn't the U.S.A., officially gain independence in 1783 and not 1776?

That is true, however, nobody recognized British rule since 1776, so unofficially, the U.S. was independent from Great Britain since 1776. Yes, the history books of each country usually talk mostly about the good things, but the British Empire did a lot of good in the world too. Don't forget that.