I agree with Mary-Lou that you shouldn't lay all the blame on the length it took to get your Masters. Part of the problem seems to be that you feel very insecure because of that, and don't have an answer ready for this question. This lack of confidence is likely more of a problem than the delay itself.
You need to own that delay, and be able to explain it. Any answer is better than silence, because no answer makes you look unprepared, indecisive and not confident.
Also, keep in mind, your program was a two-year program, so comments that people did it in one can be easily parried by saying it was a two-year program. In addition, you mention that you worked a full year, which to me seems quite long for a two-year Masters program, and I guess that is longer than would be normal for the program. And that one full year of working is relevant work experience. Own that.
As to the delay, describe the circumstances, that you were new in the country, that your supervisor moved to the States and left academia, and that this made things harder because of the distance and lack of direct interaction and feedback. Mention you couldn't find a replacement supervisor because of your topic. Own that you struggled to make progress, but especially own and focus on the fact that you completed with success! This is not a bad outcome, and you should view and tell it as an epic tale with you as the hero.