The title of "most bought car in the US" depends on how you define "bought". Are we talking about individual sales to consumers, or total sales including fleet sales? And what time period are we looking at? The rankings shift slightly year to year.
However, consistently near the top and often cited as the most popular are the Toyota RAV4 and the Honda CR-V. These compact SUVs frequently alternate in the #1 and #2 spots depending on the data source and reporting period.