The first American film to use the word "Fuck" was M*A*S*H (1970). (Interestingly, a 1979 episode of the TV series M*A*S*H included the first use of "son-of-a-bitch" on US network television.)
Below is a Wikipedia list of the top ten "non-pornographic, English-language feature films" with the most spoken uses of "fuck." Unfortunately, one of the page's editors insisted on replacing the prior delightful descriptor of "Fucks per minute (FPM)" with "Rate (per minute)." Fuck that—FPM is the metric that matters most.