What is the background investigation of the FBI in the United States?

One of the differences between the United States and China is that the local governments of states (equivalent to provinces) and counties/counties/cities are not subordinate to the central government (called the federal government in the United States). States and even cities in the United States have their own local laws, legislation and law enforcement agencies. So you can probably see in the news that some provinces and cities do not support federal government agencies to enforce the law (arrest illegal immigrants, deportation, etc.). ).

Some jobs that require criminal background checks must be completed through the FBI. The FBI has a crime database, including the identity information (such as fingerprints) of all legal immigrants. If you immigrate to the United States or apply for an American visa, enter the country, etc. They will take fingerprints and compare them with the database to see if you have a criminal record.

This kind of investigation is normal in the United States, and all immigrants have to go through this level.