The ongoing pandemic disease COVID-19 has caused worldwide social and financial disrup- tion . As many countries are engaged in designing vaccines, the harmful second and third waves of COVID-19 have already appeared in many countries . To investigate changes in transmission rates and the effect of social distancing in the USA, we formulate a system of ordinary differential equations using data of confirmed cases and deaths in these states: California, Texas, Florida, Georgia, Illinois, Louisiana, Michigan, and Missouri in the USA to be able to investigate changes in transmission rates of the outbreak and effect of social distancing . Our models and the corre- sponding parameter estimations show social distancing reduces the transmission by 60% to 90%, and thus obeying the movement restriction rules plays a crucial rule to reduce the magnitudes of the outbreak waves . Our analysis shows the current management restrictions do not sufficiently slow the disease propagation.