I agree that this is a broad question, so I will give a similarly broad answer. Crime in America is mostly linked to poverty. Some crime, such as white collar crime, mostly comes from greed. However much of the crime we see comes from desperation. In many neighborhoods, young people join gangs instead of joining the workforce. Gang crime is not the only crime linked to poverty. Prostitution, drugs and burglary or robbery are also connected to desperation. Until we increase the opportunities in these neighborhoods, crime will continue to grow.
I think that crime in America is evolving over time. Look at all the crimes committed by using technology compared to years ago. It is now possible for someone to sit at a computer and spend hours until finally hacking in to someones bank account. The Internet is used by criminals to lure victims to the place of their death. It provides for a huge challenge to law enforcement.
In order to get an answer that would be more useful to you, it would be better if you could tell us more about what exactly you are asking. This is a very vague question and our answers might not be what you are looking for. This question will probably get moved to the discussion section. Perhaps you could post a clarification.
One way to think about crime in America is to say that its importance is exaggerated in the media and, therefore, in the minds of most Americans. Statistics show that Americans' fear of crime is not really in proportion to the actual amount of crime that occurs in the country.
There are a number of possible reasons for this. One is that crime stories are easy for the media to report and easy for people to understand. Because of that, they get reported more often and people pay more attention to them. This causes people to think there is more crime than there truly is.
A more cynical approach is to say that Americans have a disproportionate fear of crime because of the link in many Americans' minds between crime and race. This link is played up by many politicians who run on law and order platforms. Because Americans fear nonwhites (this theory goes) they fear crime more than they would if more of the crimes were committed by whites.
Again, clarification would make it easier for us to give you answers that really would be useful to you.