The Department of Homeland Security is responsible for the public security US citizens are entitled to. They are in charge to counter anything that threatens the safety of the US. The bounds of their service includes:
- counterterrorism
-Border security
-aviation security
-cybersecurity
-national figures security
-maritime security
-port security
-immigration law enforcement
-detection and elimination of biological & nuclear threats
-etc
The DHS is important to maintain security throughout the US. Responsibilities such as aviation security can be traced by to 9/11, where the failure to detect public hazards resulted in a disastrous catastrophe. Political figures and the President needs to be protected in order to carry out their dedicated purpose to their nation and avoid events such as the assassination of President Lincoln or President Kennedy. Enforcements of DHS are also seen at the borders of the US, guarding any pathways that infringe on the laws of the US. More recently, cybersecurity are also a major security effort as the nation enters into a digital society. Many malicious digital intents could be a major threat to the security of public safety.
There are more factors as to why the Department of Homeland Security exists, but I hope this helped :)
