Pete,
1) If the Americans have in their force say 1xFAO, 2xHQ & 1xCO. In the American turn the FAO fails in his attempt to call in the artillery, can the 2xHQ & CO in turn try to call in the artillery until it arrives, if they meet the siting rules?
2) If the American HQ's and CO have been used to call in artillery, can they role their Command Phase dice with no penalty?
3) If a American HQ or CO fails calling in the artillery, can it still issue orders in the Command Phase?
Regards
Greg