So the other people didn't really die?
Convictions often lag the event by several years. Eventually they must appear in the statistics of another year.
Still, to address the point you have made, SeaBreeze, the discrepancy in the UK figures caused by not including deaths without a conviction is 13 - 15 %, which means that the UK figure could be taken as 1.15 instead of 1.0. Comparing that with 4.7 for the US, I think my point about the relative levels of deadly violence still stands.
The biggest problem we have over here is women (and sometimes children) being killed by their intimate partners or ex partners. We are seeing a surge in these killings and the rate is now roughly two women killed each week (2015). Money and resources have been allocated to addressing the problem. Not enough - it is only 100 million which is less than 11 days of bombing operations in the Middle East - but it is a start.
Domestic violence has gone from being something that no-one talked about to being something that everyone is aware of and wanting something to be done to prevent it. Our previous PM cut the budgets for women's refuges and support for domestic violence sufferers but the new one is much more receptive. I do believe that there comes a moment in time when entrenched problems can be addressed, but before that happens, a lot of talking has to occur. The problem must be recognised and named. And owned.
This past year, the Australian of the Year is a woman whose husband beat their son to death in front of her using a cricket bat. This happened in a public park in front of all the other children at cricket practice. Rosie Batty has done nothing else but talk about domestic violence this year and people have listened to her. That is the other end of the equation - there must be people who speak out but there must also be ears, minds and hearts open to hearing the message.
https://en.wikipedia.org/wiki/Rosie_Batty