After the introduction of television, why would some people think that there is violence and crime everywhere in the world?

Although I believe the other answer is true I think there is a more accurate response.

Before television information would travel very slowly, either by word of mouth or only as fast as the current transportation (i.e. trains and cars).

But with television information could be transferred in a matter of seconds from the broadcasting station to your televisions!

Well this allowed for information from other countries to flow in at a much faster rate, allowing for more information. The same idea refers to even within your own country. So the amount of violence has not truly changed it is just much more visible.

There is also a huge bias at play. Negative news gets more attention and sticks more to you because of the emotional reaction you have. To gain more viewers, in turn money, news company’s focus more on negative news.