You can protect your brand under the Lanham Act if you have a properly structured US trademark. This law, enacted in 1946, gives you the right to go after illegal sellers advertising or selling your products using your trademark.
Working with a brand protection agency with a sufficient legal background will give you confidence that they can go after these unauthorized sellers and impose lawful penalties.
However, this act is only valid in the US. A US trademark won’t prevent unauthorized sellers from distributing your product in other countries. Your best course of action is to know those countries' trademark laws and register your brand accordingly.