INSIDE STORY - What are the roots of gun culture in the US?

Americans are in mourning after 29-year old Omar Mateen walked into a gay nightclub in Orlando and shot 49 people dead. The alarming frequency with which mass shootings occur in the U.S. does little to blunt the trauma of each act.
But the facts of the case raise uncomfortable questions for those who seek to defend the country's gun laws. Mateen carried out the bloodiest mass shooting in recent history, despite being on the FBI's radar.
He was investigated at least twice for suspected ISIL sympathies. But had no trouble buying a military-style assault rifle. A weapon that has been used in several mass shootings in the U.S. 
The number of gun-related deaths in the U.S. are high, especially when compared to the rest of the world. Americans make up less than five percent of the global population, but they own more than 40 percent of the world's guns.
But why is it easy to access and own guns in the U.S.? And what's preventing change to laws on gun ownership?

INC News, 14/06/2016 - source:  ©AlJazeera