[quote=@Dead Cruiser]
[@CaptainManbeard] I don't think Terra would have bumped into America at any point prior. She doesn't live on Earth.
[/quote]

Hmmmm. We need to think of a way for Terra to have been exposed to America's Traveler Aura when she first got her powers, otherwise, the Sentinels would not have a reason to capture her. America's exploits across the Multiverse weren't reserved just for alternate Earths - it's possible she bumped into Terra when she arrived on her planet by mistake. Perhaps the fabric of spacetime was bent in such a way that Terra's planet - Viltrum, I'm assuming - sat in the same multidimensional coordinates as the Earths America had visited up until that point. Maybe it was that encounter that made America realize that many of the alternate Earths were at different coordinates across the multitude of folds in the fabric of spacetime.