//-------------------France payment only-------------------------

add_filter( 'woocommerce_available_payment_gateways', 'allow_france_only' );

function allow_france_only( $available_gateways ) {
if ( is_admin() ) {
return $available_gateways;
}
if ( WC()->customer->get_billing_country() != 'FR' ) {
unset( $available_gateways );
}
return $available_gateways;
}

add_filter( 'woocommerce_no_available_payment_methods_message', 'no_payment_text' );
function no_payment_text( $content ) {
//your changes here
$content = "Commande en France uniquement";
// Returns the content.
return $content;
}