The American face customization will revert to the default item when the campaign changes.
Specifically, customizations purchased in the “Normandy & Bulge” campaign will not be available in the “Pacific & Tunisia” campaign.
The same applies in the opposite case.
For example, if you change a soldier’s face in Normandy, it can only be used in Normandy and the Battle of the Bulge. When you go to the Pacific and Tunisia, the default face will be restored.
This does not happen for British in the same faction, Soviets and Germans also retain their face customization even if the campaign changes.
I know the rule about clothing customization is that it must be purchased for each campaign, but not for the face. Only Americans are bugged.
Hopefully the developers will fix this soon. 