London is a big, sprawling metropolis, with extreme wealth and extreme poverty crowded together, and all the opportunities for crime that goes along with that. I grew up in Hackney, which is one of those now-gentrified-but-f*ing-scary-in-the-90s kinds of an area (parts of Brooklyn would be a good comparison, maybe?), so I got good at doing that inner-city hood-up keep-out-of-everybody's-way thing... The whole of London is not like that by any means - the western parts of the city are generally really safe, as are the tourist spots.
I'm in France now. Come! It's glorious :)
Oddly enough, you've picked another part of another city that I'm not aware of: I've never been to the US. :) I see what you mean. I recall stories of what Russia used to be back in the 90s, after the Union collapsed (people being threatened with a gun right in the street after dark) - sounds rather similar to what your hometown had. It would be great to visit France now! Yet, there are things I'd rather accomplish beforehand, like publish my damn stories already or finally step into the university - all the things that will lead to me being able to support myself while on the journey, in one way or another.
D'oh! I assumed that, because you were on the internet, you were obviously American (and male, and in your early 20s. I make this assumption despite being none of these things myself...)! Where in the world are you?