Who runs NATO? is it the US since it is the hegemonic power?

In the modern unipolar world US is the hegemonic power, economically as well as militarily. Does US use NATO as a tool for ensuring security in European countries (explaining the eastward enlargement) while it can focus on setting up military bases in European as well as non-NATO states for security reason. In addition, since US contributes the most money to the institution and has more troops active than any other NATO member states, does US then have the upper hand?