All the semantic nonsense aside, the question is whether the U.S. cannot lose money by giving it to Argentina because they cannot go “bankrupt”.
Either the meaning of bankrupt is one which doesn’t apply to countries, in which case it’s a complete red herring to the question of whether an investment in a country can lose money, or we use a looser definition of the term “bankrupt” which the responder generously did that would allow a country to go “bankrupt” and an investment in it could lose money.
Either way, the only useful claim, that the US cannot lose money by investing in Argentina is almost certainly false.