Anyone foreigner who is going to travel to the US and visit New York City, New Jersey, Chicago and many other places...
without taking precautions, can easily wind up mugged. It is not a myth. It is not just something on TV and in the movies.
Most of us here in New Jersey have been mugged at least a few times in our lives.
Other countries warning about travel to the US are definitely not exaggerating.
Now, that being said, the vast majority of the US is quite safe. Almost all the problems are centered in inner cities.
And, if you know what you are doing, you can go to those places also and stay safe.
If you are going to travel to the US and are concerned about safety, by all means contact your government and ask for advice...