Alzheimer's disease (AD) is marked by progressive cognitive decline and memory loss, due to the abnormal accumulation of amyloid-beta () plaques, followed by tau pathology, and a gradually spreading pattern of neuronal loss. Understanding how amyloid positivity affects the brain's neural pathways is critical for understanding how the brain changes with AD pathology. Tractometry offers a powerful approach for the , 3D quantitative assessment of white matter tracts, enabling the localization of microstructural abnormalities in diseased populations and those at risk. In this study, we applied BUAN (Bundle Analytics) tractometry to multi-cohort diffusion MRI data from a total of 1,908 participants: 606 participants in ADNI3 (Alzheimer's Disease Neuroimaging Initiative Phase 3) and 1,302 participants from the HABS-HD (Health and Aging Brain Study-Healthy Diversity). Using BUAN and along-tract statistical analysis, we assessed the localized effects of amyloid positivity, potentially mediated by tau, on white matter pathways, with amyloid positivity quantified via amyloid-sensitive positron emission tomography (PET). BUAN enables tract-specific quantification of white matter microstructure and supports statistical testing along the full length of fiber bundles to detect subtle, spatially localized associations. We present 3D visualizations of tract-wise amyloid associations, highlighting distinct patterns of white matter degeneration in AD.