You can complete this achievement in Chapter 3 of The Road to Indepedence.
How to Obtain Master of the Americas Achievement
Take the 8 out of 8 regions you need for completion of the objective, but keep in mind not to have over 14 regions in summary.
Leave 1 region, of the 8 needed for the main objective, to rebel. Destroy every building, remove your units from the region and raise the taxes for the nobility to level 4. Wait a few turns and a rebel army of British Colonial will appear and claim the region.
After that, conquer all the provinces on the map.
As your last step, conquer back the rebelled region you left on choice at step 2.
You are now the Master of the Americas.
I recommend Georgia for the rebelion. So you can keep an eye on her and be in close distance.