Every form of intellectual property (patent and trademark) is granted by a country, for use only in that country.  A U.S. patent will protect against a competitor making, using, selling, or offering for sale in the U.S.  If they make it in China, and sell it in Europe, they will not infringe (although they will infringe if they try to sell that product in the U.S.). If you want to protect your invention in another country, you must file in the other country (or countries).

For patents, a U.S. application does establish international “patent pending” status throughout almost the entire world for up to one year.  So you don’t have to worry about international protection right away.  When the one-year anniversary approaches (typically about 10 months after filing), you should discuss foreign filings with your Attorney, and determine if you would like to file for foreign patent protection.

Foreign filing is expensive and complicated, so this is definitely a topic you should discuss with your attorney when the foreign filing deadline approaches.