Ecosystem respiration (RECO) constitutes a substantial component of terrestrial carbon fluxes and strongly influences terrestrial carbon budgets; yet its variability across ecosystems and sensitivity to environmental drivers remain poorly understood. The objective of this study was to quantify the magnitude and variability of RECO, heterotrophic respiration (RH), and autotrophic respiration (Ra) in relation to key environmental drivers and identify the environmental thresholds at which maximum RECO occurs using AmeriFlux and Soil Moisture Active Passive (SMAP) mission Level 4 Carbon (L4_C) remote sensing data. Our findings reveal clear seasonal and spatial variations in RECO, with higher rates observed at eastern and lower-latitude regions of the conterminous US. However, exceptions highlight the influence of factors like extreme heat and limited precipitation. For example, the US-Wkg (Arizona) and US-Mpj (New Mexico) sites showed low RECO despite being in a high-temperature region. The AmeriFlux sites exhibited notable differences in the statistical distributions of RECO, including maximum and minimum, quartiles, and outlier values. RECO, RH, and Ra exhibit a strong association with air and soil temperatures in the US-ARM (Oklahoma) and US-Ne1 (Nebraska) sites while soil moisture showed a better correlation with RECO, RH, and Ra at the semi-arid US-Wkg (Arizona) site, suggesting no universal dominant driver. Environmental threshold analysis indicates that RECO generally peaks at soil temperatures of 16-25 degrees C and air temperatures of 13-31 degrees C across most AmeriFlux sites. Precipitation, however, shows inconsistent effects. The RECO derived from the SMAP satellite product clearly shows seasonal and spatial variations in RECO, RH, and Ra, and it has good correlation with the RECO of some AmeriFlux sites. Understanding these dynamics in RECO using AmeriFlux and satellite data is non-trivial for developing ecosystem-specific carbon emission reduction and agroecosystem management strategies, contributing to theoretical ecology, applied climate science, and sustainable agriculture.