If you are using your trademark abroad or authorized someone else to use it abroad, then you may encounter issues with goods authorized in those countries being sold in the United States. If this happens and the trademark owner did not authorize it, then the good would be considered gray-market, or parallel imports. Such goods will not be considered counterfeit as they are technically legitimate goods. US Customs Service can assist with enforcing your rights if such infringement occurs. To do this, make sure the trademark is registered with Customs. Private action can be sought if this is not enough. To obtain relief there are many factors such as whether the goods are genuine, contain material difference, if material differences are allowed on goods sold in the US, variance in quality control, and others. Material differences are not only physical may include things like different ingredients, labels, quality, language, etc. Your trademark or trademark application bestows valuable rights regarding what and where goods are sold. Understand your rights and be proactive with enforcing them.
This blog is not legal advice and is not specific to your application. You should always consult an attorney.