Using Stamen Toner map

I’m wanting to use the STAMEN_TONER tile to plot some markers around the United States.

So I followed the example from this youtube video: https://www.youtube.com/watch?v=YAls_da1cF4.

I have the map showing up and I have points showing up where I want them to.

Does anyone know how to make the map just focus on the United States? Right now it defaults on the latlng point (0,0).

Thanks in advance