You can't duplicate announcements. If you are working in Courses it is possible to import announcements from one to another just like you can import any content.
But what I would probably do is to simply copy the text from the first announcement I create and then create it again in the other courses or groups.
Hello there, @jm_vegas ...
To piggy-back off of what @rmurchshafer has already told you... if you use the instructions given in How do I select specific content as part of a course import?, you can essentially copy content from a course into the same course. As you follow the directions in that Guide, you'll be logged into your course, and then when it comes time to selecting the course, choose the exact same course that you're already logged in to. You may get a message that says you're selecting the same course, but that's ok. Just keep following the directions, and then select specific content...that is, select the announcement you want to duplicate. The course import tool should make a duplicate of that announcement for you that you can modify for your needs. I hope this helps!