I'd agree that if the character of the city isn't particularly important then I would be wary about investing too much time and money in portraying it's soundscape. However, I'm intrigued how an animation could be set in such a specific location as Vienna and it not be necessary, at least a few times, to evoke a sense of place.
For Kickass, I needed to provide a New York backdrop but it didn't warrant a recording trip to the States as we knew the director preferred very clean soundtracks rather than lots of busy (or potentially distracting) atmos FX.
However, despite this, I still wanted to get some fresh authentic ny sounds for when a sense of place was called upon, however infrequently (I had good sirens and stuff but was relying a little too heavily on cititrax for good street voices / shouts). That's where this amazing online sound community that seems to have flourished over the last few years comes in! Basically, track down someone from that area (agreed, Vienna may be harder than NY but not impossible surely) then either trade fx or pay a relatively small amount (compared to foreign travel, that is) for them to get some sounds in their own backyard! I talked in a bit more detail about this in a post a while back:
However, even if you don't go this far, plain old research on the Internet about the city itself can throw up all kinds of ideas about what the city is really like, eg. What kind of transport? Trams? Is there a subway system? Heavily pedestrianised? Even if the atmos isn't that important I tend to do this as at the very least it gets the creative juices going and at the very most it helps make sure you don't put in an incorrect sound that people WILL notice!
Apologies for the perhaps long-winded answer: In a nutshell, as the world gets smaller, authenticity is more easily achievable than ever before, so why not make it part of your creative journey, even if (as in the example of Saving Private Ryan that you mention) it isn't the exclusive and final destination?