In North America can someone copyright the performance of a magic trick?

copyright requires a fixed form, so it does not apply to performance. a process can be patented, so you could research that angle. it is most likely it falls under the "trade secret" laws. if you can develop a process without knowing anything about how the others did it then you should be ok. however if a helper of one of the other magicians gave you a clue, then that violates commercial secrecy laws. a good example is Kodachrome process, no one has ever figured it out except from info provided by former Kodak employees, so Kodak can stop all competitors from developing Kodachrome film.

There are some elements that can be protected or copyrighted:

You can get a patent for the creation of a magic or a illusion. There are some creators that protect their inventions and especially the mechanics of the trick. Jim Steinmeyer is one of those; he kept for himself the rights of the illusions and when you buy a book from him, he allows you to build that prop or get it build by a artisan, but not to build it in large numbers and then sell it, for that you must pay him a royalty.

You can protect also the design of a prop, to avoid others to copy it.

You can get, by a commercial agreement, the exclusivity of the performance of one effect. This can be for a limited period of time or permanent. For example, David Blaine gets the exclusive rights of the TV performance (only TV) of the Healed and Sealed soda can, whichs expire this year.

The performances or presentations can be protected as a routine, like a sequences of tricks, but the style certainly is a little harder to cover. If not, check how many guys making dove magic began to dress with a purple tuxedo style, after Greg Frewin performs on The World's Greatest Magic...

If you, after watching a performance, figures out your own way to achieve an effect, you may be safe from being sued, if you can prove that your way is yours and different than the original and protected. That was what happened between the fight of PT Selbit and Horace Goldwin in the 1920's when they fought about the Sawing a Woman in Half creation.

And if you get inspired by one magician, duplicate the effect, and performs the same way and even using the speach of that magician, you shouldn't be sued... you may be kicked in the butt for your lack of originality!!!

Yes they can. You know that quick change couple on Americas got Talent? They are patenting the effect

This i want to know.