This is one of those issues that are easy for non-Americans to misunderstand. Why are guns such an issue in the USA?
It's easy to assume that most Americans have guns or are fiercely protective of their right to have a gun. Actually, most Americans do not own a gun, even though gun ownership is much higher than in most European countries. The problem is that for some Americans guns represent a uniquely American freedom. For them, guns are the ultimate guarantee of individual liberty and this freedom is protected by the Constitution. Critics of this view argue that the Second Amendment should not be interpreted as a right to own a gun and even if it is, it is outdated.
However, while most Americans do not own a gun, they do not support the kind of restriction on gun ownership we have in the UK ie a near-total ban on gun ownership. Instead, most would support some kind of 'gun control' such as a waiting time after a gun in purchased while background checks are carried out. So why won't Congress pass this kind of gun control?
At least part of the answer is the Constitution. Apart from the Second Amendment, the Constitution over represents the interests of rural states. By giving every state two Senators, the states with a culture of gun ownership have disproportionate influence in Congress. To prevent the tyranny of the majority the Constitution ensures that well-organised minorities can prevent the will of the majority succeeding. Whether in Congressional committees or in a Senate filibuster or in the Supreme Court, there are plenty of opportunities to stop legislation. The Constitution creates a bias toward inaction.
In 2016, four months after the Sandy Hook school shooting- the Senate failed to pass the Manchin -Toomey Amendment ( Joe Manchin, D-West Virginia and Pat Toomey,R-Pennsylvania) which would have required background checks. Congress also did not renew the ban on the purchase of assault rifles which had been in place from 1994 until 2004 when it expired. Attempts to renew it have all failed even though it is supported by a majority of Americans.