What is the biggest problem facing police in the USA today?

Detailed description of the problem.
Why is this the #1 problem? (More important than any other at the this time.)
Related issues.
Explain how this does or could affect a police agency (directly/indirectly).
Who’s responsible? (The major players.)
What is the history of this problem?
Is it something new or has it been a problem for a long period time?
What’s been done in the past, if anything?
Why did those efforts work or not work?
What is the long-term strategy for addressing the issue?
Final recommendations.
Why should we care? (Police chiefs, citizens, government officials, etc.)
Whatever information you believe would be of interest.