"England has lost."
Translation:Mae Lloegr wedi colli.
There is a difference in the meaning 'Mae Lloegr wedi colli' is something that is complete and over. 'England has lost', the event has finished. 'Roedd Lloegr yn colli' is 'England were losing' at sometime in the past but it doesn't tell you the final result. eg 'England were losing in the first half' = 'Roedd Lloegr yn colli yn yr hanner cynta', but they still could have won at the end 'Mae Lloegr wedi ennill' or they could have lost 'Mae Lloegr wedi colli'.
Are you suggesting that as an alternative? Because that would be "England was losing".
I'd also been taught that Roedd was "has", I'm fine with being wrong if I am.