"What can you do in America?"
Translation:Beth dych chi'n gallu wneud yn America?
Does the next word soften after medru? I didn't think it did (it doesn't in the SSiW course, at least). And what about gallu?
The full sentence is 'Beth dych chi'n gallu ei wneud yn America?', the personal pronoun 'ei' softens the verb 'gwneud'. Literally it means:- 'what can you do 'it' in America'. The 'ei' refers back to the question 'beth'. In speech the pronoun is generally omitted but the soft mutation stays to indicate it's importance to the sentence.