How can insurance improve a nation?

This is a very broad question, so only a general answer seems appropriate.

The nature of insurance is that it permits a person or a business to transfer the risk of a financial loss from him/her/itself to the insurer. The extent of the risk transfer is defined in the terms of the insurance contract.

Were it not for the existence of insurance, the individual or the business that caused or incurred the financial loss would have to bear the brunt of it.

Another benefit of insurance to a nation is that insurance is a major financial indistry. Therefore, it is the source of employment, on many levels, to many people. Those people are not necessarily all employees of a specific insurer. Instead, there are third-parties that perform functions for insurers that also employ many people.