1) Sure it does. In the UK street gangs use knives because guns aren't sold at Walmart. The real bad guys have guns sure, but 14 year olds rarely gun each other down in the street like in the US. We have an epidemic. Other first world countries with sensible laws do not, but of course its not a magic fix all.

2) Racism does not cause the killings, but it makes it harder to succeed in school when the teacher may believe less in you inherently. Jobs may stop at interviews. You may be called names in the street or avoided while you're just playing with your friends. Black people aren't inherently violent. There are more black kids in gangs because they don't go to live cushy lives that make being in a gang not even a consideration as the wealthy do