Hey there! I'm happy to help!
The IRS collect your taxes; they don't have anything to do with security.
The culture is the traditions and common habits of the people. Culture is not a government organization so it does not really maintain order or ensure security.
The monarchy is basically the royalty or nobility. They rule the country but usually the king himself does not ensure security for his citizens.
The Government is what protects people's rights, ensures their security, and maintains order. There are many government systems set up to secure all of these rights.
I hope that this helps! Have a wonderful day! :D