Then, and only then, the country

Once the field is set, the country question becomes answerable, because it has criteria. Which countries have real depth in this field — not one famous university, but a cluster of them? Where is the industry actually located? What does a graduate in this field earn there, and what does it cost to get the degree?

Sometimes the answer is the country you first thought of. That is fine. The difference is that now you can say why, and so can your parents.