This study aims to demonstrate differences in the efficiency of municipal waste management from 2014 to 2017 between two selected cities with a comparable number of inhabitants: Radom in Poland and Spokane, WA, in the United States. The study considers the significance of these cities’ rates of waste accumulation and the application of the autoregressive integrated moving average model for forecasting. Within a 4-year period, Spokane recorded a higher total mass of waste collected (4175.4 Mg) than Radom, while Radom recorded a higher monthly average (exceeding 500 Mg) than Spokane. In these cities, nonselectively collected waste was predominant, with an average mass of 1340 Mg, and the highest accumulation rate per capita in the European Union was recorded in Radom (174.04 kg per year). An increase in the number of residents by 2000 people in Spokane fostered an increase in waste accumulation rates per capita by an average of more than 11 kg per year, with the highest value of selectively collected waste accumulation per capita reaching 102.18 kg per year. In comparison to Radom, the Spokane city waste management system is characterised by projected waste growth, greater efficiency, a higher accumulation of selective waste, and rational waste to energy processing. Generally, the results of this study indicate a need to develop rational waste management, while taking into account the principles of sustainable development and the requirements of the circular economy.