Those six countries were outrageous!
Gordon and Henry were kind enough to warn them of the impending crisis. Instead of thanking Moon, they wanted to blackmail the country. Anyone would be angry.
They were bullies!
If the two of them were the selfish type, they would never have told the other countries about it.
It was just money. If Moon were to empty its treasury, it should be able to cover the cost.
There should be enough money to purchase all the materials from other countries. They should be able to build the space cannon and the shelters. In that case, other countries wouldn't have time to build shelters.
After the catastrophe, there wouldn't be many people left on Earth. By then, the Moonians would be the only survivors on this planet. The country could owe the entire planet.