I am using Google Calendar on an up to date iPhone 4S. I also use my iCloud calendar.
When I create an event in the Google Calendar in iOS's calendar app, the event is only visible on the iPhone. It does not get synced to the Google web app or my Mac. When I create an event on the web app, it gets synced to the iPhone.
Using the iCloud calendar works fine both ways.
What might be the problem? I've tried to disable the calendar syncing, and re-enabling it, but that did not help.