Invasive species are a major threat to biodiversity and tree squirrels (Sciuridae) are among the most successful mammalian invaders. Two species native to the eastern United States, the eastern grey squirrel (Sciurus carolinensis) and fox squirrel (Sciurus niger), have been repeatedly introduced into the western United States. The non-native species have expanded their ranges extensively, negatively impacting the only native Sciuridae species in the western United States, the western grey squirrel (Sciurus griseus). While numerous studies have documented the impacts of these invasions on S. griseus, few have assessed the potential for future expansion, and none have simultaneously evaluated all three species. In this study, we use citizen science data from the iNaturalist database to model the distributions in the western United States for all three Sciurus species. We generated models based on occurrences in the squirrels’ native ranges, compared to models generated from their introduced ranges, and evaluated current and predicted conflict zones. We determined that the greatest potential conflict with native squirrels is in areas adjacent to regions of high human footprint. As human development expands, the invasive squirrels are likely to expand into previously inaccessible areas, increasing conflict with and potentially displacing the native western grey squirrel.