A country singer does not pick a key to be difficult. They pick the one their voice sits best in, and the guitar chair's job is to get there without losing the ringing open strings that make a chord sound like a chord. Five shapes — C, A, G, E and D — ring open on a standard-tuned guitar without a barre; three more — Am, Em and Dm — do it in minor. Everything below is which CAPO FRET turns one of those shapes into the singer's actual key, computed rather than typed.
This page never prints a fret-by-fret capo chart on its own — that table already exists, properly, on sister sites, and the doors below point at them. What is native here is narrower: for each of the twelve keys, which capo positions (0 through 5 — nobody capos a country song at fret 9) land an OPEN shape.