If a URL points to a KML file, you should be able to pass it to the KMLLayer class to create a layer from the KML. See the simple KML Layer sample for an example.
Yeah, that's what I was using, but it doesn't seem to work. I can get it to work using the KMLLayer class using the Flex API and according to this thread http://forums.arcgis.com/threads/40348-Display-layer-based-on-Google-Fusion-Tables it works with silverlight. So I was just wondering if anyone has had success using the API for Javascript.