The reasons for the United States invading Iraq were complicated, but the major ones at-least were because the US believed that Iraq posed a threat to the peace of the west and the belief that Iraq had large quantities of poison gas and possibly a nuclear weapons program. If left unchecked, Saddam Hussein and Iraq could have become incredibly dangerous with the knowledge that Saddam Hussein possessed weapons of mass destruction.
On the other hand, there are many reasons the United States shouldn't have invaded Iraq. The belief that Iraq possessed weapons of mass destruction wasn't confirmed. While Iraq could have had control over biological and chemical weapons, the existence of a nuclear weapons program would have been far harder to hide.
On the other hand, there are many reasons the United States shouldn't have invaded Iraq. The belief that Iraq possessed weapons of mass destruction wasn't confirmed. While Iraq could have had control over biological and chemical weapons, the existence of a nuclear weapons program would have been far harder to hide.