What role did the Skrull invasion play in the backdrop of the 'Civil War' storyline?

While not the primary focus, the looming threat of a Skrull invasion (which would fully unfold in the 'Secret Invasion' event) added tension to 'Civil War'. The Skrulls' ability to shapeshift and infiltrate heightened paranoia and distrust, making it harder to determine who could be trusted. Iron Man argued that registration was necessary to identify and control potential Skrull infiltrators, further fueling the conflict.