But if you read/listen to the news, talk to the people or just overhear their conversations in the streets, you'll probably perceive the difference and get to look at the place with different eyes.
I think this difference is deeply rooted in history and is a clear continuing legacy of the iron curtain.
Its interesting to see how attitudes diverge when populations split anyway.
As an aside you touch on a separate point: it's much easier for your girlfriend to find work in Belgium than it would be for you to find one in Bratislava. Which probably explains, much like here further south, the mass exodus of the youth and a somewhat pessimistic attitude of the locals towards their country's economy.
Depends on what you mean by "third world conditions" too. There are places in the third world that are heaps and bounds above some US towns and cities.
Try parts of Mississippi, Appalachia, etc. Or heck, try Pine Ridge SD, where life expectancy "in 2007 was estimated to be 48 for males and 52 for females."
It's nowhere near comparable to Latin American slums, obviously, but it certainly looked on par with what you see in the Belizean or Mexican countryside. And it was a far cry from what I've ever encountered in rural France, Benelux, or Germany outside of abandoned crack shacks.
As one who actually lived or traveled to several of those places, I'd submit that the answer is quite a few things.
There's surface level resemblance between the two lists when you're in a shopping mall or a shop heavy district. Outside of the latter, however, Western cities and countryside stand out as much wealthier in all sorts of ways. In particular less places that look like they're in shambles.
The contrast is comparable what you can encounter in the US countryside (which at times is borderline 3rd world-ish) vs e.g. major US metropoles (which compare to major Western European cities in sophistication and wealth).