U.S. laws give many rights to citizens as well as non- citizens. But certain privileges go only to the citizens. As a U.S. citizen, you have the right to vote in the federal elections. Another major advantages is that, you can reunite families. You can bring your loved ones to be with you. You can bring your fiance through the K1 visa or bring through your spouse and children under the K-3,K-4 category. US citizens with unmarried children under the age of 21 can sponsor them as "Immediate Relatives". Only U.S. citizens can sponsor their parents for a green card. Additionally, your children may be eligible for US citizenship based on parents' status as a US citizen.
Being a U.S. citizen, there is no restriction for you to enter/ exit the US. The time you spend outside of the U.S. is not restricted. And it is also convenient for travel as certain countries do not require visas of US citizens. Another added benefit is that only a US citizen can apply for a US passport. Having a U.S. Passport, you can get assistance from the U.S. Government when you are overseas. You also will be eligible for federal jobs in the US. and can also become an elected official.
If a Legal Permanent Resident (LPR) is accused of any illegal activity, there are chances where he/she can be deported. Whereas as a US citizen, you have the right to an attorney and a fair trial and need not face the hardship of being deported. These are only a few of the advantages of US citizenship and does not include all.