If correlation proved causality, your statistics might actually mean something. I could also easily say that gun control results in more murders because the cities in the US with the greatest gun control laws in general have the highest percent of murders. In reality, while this may possibly be a result of tighter gun control, it is also the case that gun control laws were enacted BECAUSE these cities had high murder rates. The fact that they did not work or made things work is only part of the story.
A better question would be if murders went down significantly in countries that banned guns after the ban. They did not, and in fact the opposite happened.
Since Canada passed strict gun control laws, their homicide rate has gone up while at the same time going down in the US:
In England, people injured by firearms has increased by 110% in the 10 years leading up to 2008. (Ban was enacted in 1997). In late 2009 The Telegraph reported that gun crime had doubled in the last 10 years, with an increase in both firearms offences and deaths.
UK Gun Statistics
Australia did not ban guns, but has seen mixed results with their efforts to reduce the amount of guns owned. Accidental gun deaths are up, gun suicides are down with other suicides are up by the same amount, and assault rates are up. Gun robberies increased for the first 5 years but are now back down to the levels they were before the gun buyback program.
So comparing gun deaths in the US to countries that already had much lower gun deaths before the ban guns is obviously an irreverent comparison for this debate. Violence in the US is a complex issue, and one that will not be solved by more gun control laws. As long as one group of people is always blaming others for the problem, we will never get a handle on how to change our culture to reduce the attractiveness of violence in the minds of our children. For that to happen, we need to co-operation of parents, government, the media, Hollywood, etc. Unfortunately, that is unlikely to happen, because in my mind the biggest problem is children growing up without fathers being raised by TV, movies, and "music" artists which promote violence. As long as the government pays people to have children and pays single mothers to stay single and poor, this is not going to change.