The question of what countries to file for invention protection: always a hard one. There is normally a timeframe (6 months to a year, depending on whether you have filed a utility patent or a design/trademark) in which one has to make the decision, and there are no do-overs.
I present some considerations to help stir up your innate decision-making process.
For a North American company, the US is the biggest market and an obvious choice. Furthermore, the USPTO acts quickly to provide feedback on patentability. Canada is the other North American market, and the costs of patenting are relatively low, making it an easy decision for most businesses.
Mexico and the South American markets may be useful if you plan to do business further south. I recently had a patent go to grant in Mexico after a fairly reasonable prosecution, which is promising. Brazil is a large and sophisticated market.
Look at where your product will be or might be successful, or where your competitors operate, and file there.
Crossing the oceans, we find mega markets in Europe and Asia.
For Europe, Germany, France and the UK are large markets, and might be your first tier if budget is limited. Traditionally, I prosecute European patents through the EPO and once granted, the invention is “validated” in each of about 28 European countries. For designs and trademarks, there is an even easier process in Europe. One application will do it all.
Caveat: Be careful not to assume that a country is covered by a community application in Europe – Norway is still outside of the fold.
Also, bear in mind that France, Germany, Luxembourg, Monaco, Switzerland/Liechtenstein and the United Kingdom do not require translations into their local language upon validation. This is a consideration if you are on a budget and trying to decide which countries to validate your European patent in.
Asia is an important market with an increasingly sophisticated patent tribunals and court systems. S. Korea, PRC (China), and Japan are the first tier. Second tier could include Singapore, Vietnam, and Thailand, and India.
The middle east is another market that may interest you: Israel, Egypt, Saudi Arabia, Qatar, Oman, Bahrain, and the UAE are potential jurisdictions.
At the core, consider filing in depending on where you will be selling and where your competitors are, and how long you want your patent list to look: Australia, New Zealand, the Philippines, Indonesia, and the Russian Federation.