@Murdock @CDEEKS Do you have a space behind the Faction Name? "CUP_B_US_Army " <--
That will mess your Factions up.
Can easily happen with some copy and paste work.
If that is not working, then try to use another faction. BLU_F for Starters. If that is not working, you got something messed up other than the faction itself. I'm not sure if the CUP_B_US_Army has Groups and such defined already, which could lead to that error you had too.
I have checked for spaces ,still doesn't work. The BLU_F works no problem and i have tried every single faction listed on the Wiki. It's weird because i have rolled my version back to an older version of ALIve like was suggested to me and it seems to spawn the aircraft of the custom factions but nothing else. so i am at a total loss as to what's going wrong. About 6 months ago when i was alway playing ALIVE i never had any issues like this. But i have read that due to some changes in the Code in new versions it's now not possible to use many custom armies with this mod.