According to the US Copyright office:?

"Your work is automatically protected under U.S. copyright law from the moment of its creation. Thus filing a copyright is not largely mandatory. However, filing does offer certain legalized benefits, and it is required in order to file suit for infringement."



My 2 question are: What are the benefits of copyrighting? and If I am protected under US copyright law, but cannot sue for infringement, what protection do I really have?
We have rights ? think you answered your own question ,
see copyright.gov and wikipedia articles on copyright for answers to your question.

registering a copyright allows you to collect certain statutory damages that you are not entitited to if you don't register.

you can sue for infringement either way - the ownership of copyright, wheter registered or not confers, in good health, copyright rights.

Which means the sole economic monopoly for a limited time (subject to Fair Use exemptions) to benefit from the untested,. from copies, and from derivative works.

All in the name of advancement of the Arts and Sciences, as it says right smack contained by the middle of the US Constitution.
Think in the region of it. You answered your own question.

You are automatically protected, meaning, whenever you create something, it automatically has a de facto copyright.

But, unless you truly register the work, you cannot sue for infringement. So...

If someone happens to be violating one of your copyrights, register the work. And then sue their (a)ss. The one and only difference here is that if the other person wants to contend that they're the real creator, surrounded by which case you'll need to provide more evidence that it was contained by fact your work, but only if they actually apply for a lawful copyright as well, which let's be real, most thiefs wouldn't bother to do. On that note, I would also enunciate that it would be rather difficult for most people to steal your work as long as you can show you created it, which most artists can easily do.

One more point about protection - there is no such thing as protection. The regulation doesn't keep someone from violating your rights. It just provides a recourse for when they do.