Are patents applicable worldwide? How?

Patents are only applicable in the county that issues the patent. However, there are some treaties that require the signatories to acknowledge and protect IP registered in other countries.

Patents are local only - each country has its own patent system. Your US patent protects your invention only in the USA. If you have no Canadian patent - anyone can practice your invention in that country. GOOD LUCK!

Patents are valid only in the countries in which they are registered.

Generally, a US patent will only apply to goods made or imported into the US. As to a method claim, a US patent will control practice of the method in the US or goods imported into the US which are made using the claimed method.

Patents are geographically limited to the countries in which they are obtained. So, your US patent gives you patent rights in the US alone and nowhere else. If you move to Canada, you still have the right to exclude others from making, using, or selling any product or service covered by one or more of your patent claims, but only in the US, not in Canada or wherever you decide to live. Of course, it want your patent to remain enforceable through its entire patent term (20 years from filing date), you will have to pay maintenance fees at specific times during the life of your patent. As always, you are well advised to seek the advice of patent counsel to answer any specific questions you may have about your particular patent rights.

Patents are territorial in nature and are issued by the national government of each country. Generally speaking, a Patent prevents anyone from making, using, or selling a product in the country where the Patent was issued. If I have a U.S. Patent for a new widget, no one can make, use, or sell the widget in the U.S. If someone makes the widget in China and markets the widget in the U.S., there is an infringement of my U.S. Patent. If someone makes, uses, and sells the widget in China, and the widget never enters the U.S., the U.S. Patent has NOT been infringed. A Chinese Patent would be needed to prevent this latter situation. Also, generally, speaking, to obtain foreign patent protection, the foreign Patent Application will need to be filed within one year of the filing date of the first U.S. Patent or Provisional Application for the widget. In the situation that you describe, since Canada and the U.S. share such a large border and are such good trading partners, your U.S. Patent may give you adequate protection in Canadian markets. It may be useful to seek the advice of Counsel and I hope that this helps.