Here is the answer with

6 circles.

:

I wrote a code to find a better option and I got

5

as below graph

another solution:

I believe this is optimal.

Here is the answer with

6 circles.

as trial and error:

I wrote a code to find a better option and I got

5

as below graph

another solution:

I believe this is optimal.

Note: My code works by generating tens of thousands of imaginary circles of all different sizes across the map to see which states they touch, and then it uses a Constraint Programming solver to pick the absolute smallest handful of those circles that perfectly touches every state exactly one time.

Here is the answer with

6 circles.

:

Here is the answer with

6 circles.

:

I wrote a code to find a better option and I got

5

as below graph

another solution:

I believe this is optimal.