It depends on many things including the size of the debt and to whom. In the least, it will damage the reputation of the country, make it harder to borrow in t

It depends on many things including the size of the debt and to whom. In the least, it will damage the reputation of the country, make it harder to borrow in the future, and hurt its relationships with other countries. What happens when a company defaults on its debt? Its rating goes down, reputation is hurt, etc. Same deal, except it's more global with a country.