Leaders are replaced all the time in the U.S. In fact, we have a system of government specifically designed to faciliate the regular replacement of leaders.
Our secret sauce over other nations is specifically how we select the new, very carefully hand picked leaders. Which Bush or Clinton family member will it be next time? with some help from the revolving door of actual leaders (.com) vs figurehead leaders (.gov)
I once looked into the personal backgrounds of U.S. presidents. It's about 50% carefully groomed elites like FDR, Kennedy, and Bush (both), and about 50% "rose from nothing" people like Eisenhower, Reagan, Clinton, and Obama.