Each country within the Union had its own original regimental flags right through the Civil War

https://manuelasvb291.keystonescope.com/posts/the-many-faces-of-civil-war-flags-an-overview-of-types-and-designs-3

Each state inside the Union had its possess distinct regimental flags in the time of the Civil War, reflecting local satisfaction and varied histories tied to their participation within the struggle.