A huge portion of the US is covered by purely volunteer fire departments. Communities pay for equipment and training and that is it. Response times are slow but it is really the only viable option in rural areas.

Not always slow. I had a kitchen fire at 4am from a microwave spontaneously combusting. Had the local deputy fire chief and local fire truck there within 15 minutes plus trucks from two other local towns.

At the federal level, FEMA and USDA offer extensive grants and low interest loans to fund fire districts in rural communities with a small tax base. I think basically every state offers similar funding assistance on top of that.