Most Americans say crime has gotten worse over the past decade. They're wrong. Moreover, the focus on mass shootings appears misplaced when mass-shooting deaths make up less than one percent of all homicide deaths.
When it comes to Baltimore being a haven of appalling violent crime, Trump's not wrong. Although it has strict gun control laws, Baltimore's homicide rate is comparable to that of El Salvador and Venezuela.
The United States is not a nation. From the very beginning it was more of a collection of various nations united by ideas of political unity and by fairly high levels of tolerance for other groups within that union. The US certainly contains nations, but it was never a single nation.
The theory goes like this: capitalism combines with consumerism and advertising to make us sad, lonely, and forever chasing after material goods. So we consume endlessly and the Machiavellian capitalists reap the rewards. It's not a great theory.