Patent rights in the U.S. are governed by U.S. federal laws. These laws determine what is patentable and the procedures that are required to obtain a patent.
Patent standards differ from country to country. International treaties (like the Patent Cooperation Treaty and the Paris Convention) make it possible for an inventor in the U.S. to obtain patent protection in other countries besides the U.S., but patent applications must be filed in each of these other countries and corresponding fees must be paid.
For more information, you can visit the United States Patent and Trademark Office website at
http://www.uspto.gov/patents/int_protect/index.jsp.