What is the best way to extend our US trademark protection to the rest of the world?

Generally, you have two options.

1. If you don't need to extend your trademark to many countries, you can file individual trademarks via local attorneys or a law firm. This might be a good option if you plan to register your trademark in less than five countries. One application will be filed in each of the countries of your choice. If your second application is filed within 6-months after the first one, you might take an advantage of earlier filing date through a priority claim. If you want one provider who can manage all of your applications, you can check the list of countries we cover.
2. You can file via the Madrid System using the World Intellectual Property Organization (WIPO). This way, you only need one base application - in your case, in the US. The US trademark does not have to be fully registered at this stage - pending applications are accepted by WIPO as well. The base application should cover the same goods and services that will be registered internationally. You only need one representative who will manage your international application. There is no need to appoint a representative for each of the countries where you wish to register. You will then choose the countries where the international application will be filed. You can select from 193 WIPO member states.