Mesoscale convective systems (MCSs) and individual deep convection (IDC) are key contributors to extreme precipitation across the U.S., significantly influencing local weather conditions and the hydrologic cycle. High-resolution, convection-permitting simulations often struggle with biases in representing observed features of MCSs and IDC and exhibit considerable uncertainty in projecting their future changes under warming scenarios. This study explores an alternative theoretical modeling approach to assess these future changes for comparative analysis. A global convection-permitting model simulation suggests contrasting future changes in MCSs and IDC between inland and coastal regions (see Figure). A Lagrangian parcel model is employed to isolate the impact of thermodynamic environmental profiles on convective systems and to elucidate the physical mechanisms driving these future changes. The single-column parcel model indicates a decrease in the frequency of IDC occurrences, along with an increase in duration and total rainfall under warming, attributable to rising most unstable convective available potential energy (MUCAPE), convective inhibition (MUCIN), and precipitable water (PW). The multi-column parcel model reveals contrasting changes in the frequency and mean area of MCSs between inland and coastal regions, underscoring the role of increasing (decreasing) mean MUCIN in reducing MCS occurrences over inland (coastal) regions. The increase in mean MCS area over inland regions is linked to the interplay between accelerated gust fronts and enhanced subsidence strength, further traced to the unchanged mean MUCIN but increasing MUCAPE in large-scale environments. This study serves as a prototype theoretical framework for quantifying future changes in convective systems and reducing model uncertainty.