Only someone coming from a very poor sausage culture would think that. Actually a Wiener Wuerstchen is pretty much different from a Frankfurter Wuerstchen. Both are not to be confused with a Bockwurst. So someone from Vienna who knows his wurst, would differ between a Wiener and a Frankfurter, as would the connaisseur from Frankfurt. However, an austrian would mean a different wurst than someone from (northern) germany when he speaks of a Knackwurst. An extrawurst is a type of wurst in austria, in most parts of germany it would be a figure of speech. And that's just the tip of the wurstberg...
If the american idea of a wurst is anything like their idea of beer you're probably right,. You need to buy it fresh, from a butcher shop or a delicatessen. Anything out of a tin can, a glass jar or a blister pack is dogfood at best.
Unfortunately though, you are correct. I drink German beer almost exclusively, but true German sausages are harder to come by.