I learnt English in the USA = I have learned the language when I was in the USA. This sentence makes perfect sense!
I've English in the USA = I have English in the USA, which doesn't make sense!
I've been learnt English in the USA = also doesn't make sense, unfortunately! You could say I've been LEARNING English in the USA, which means I have been learning English in the USA, as in you have been in the process of learning English in the USA. Hope this helps!