The Google+ app isn't a browser. There's no reason you should expect to be able to cut and paste an arbitrary URL into it (except for posting, of course). What should the app do if you decided to paste: "http://www.cnn.com/ or whatever?

To me, Android's Intent setup is beautiful because the apps themselves decide whether they can or can't handle particular URLs (so Google+ can catch Google+ URLs, Twitter clients can catch Twitter URLs, Google Maps can (and other mapping providers could, for that matter) catch map/location URLs, etc.).

Without the right kind of extensible framework, I just don't see how you could do anything similar and usable in iOS.