Not primarily, no, although it certainly helps with the expansion of US power, just as any collective group amplifies the efforts of the individuals in that collective. By the same token, Estonia's power is also enhanced by being in NATO.
Primarily, NATO is a defensive alliance of (mostly) liberal democracies. This fundamental isn't changed by the fact that some parts of NATO have also engaged in offensive actions, mostly, I would argue, with good intentions if not necessarily with good results.
But this is besides the original point, namely that no-one - not even Putin - believes that NATO would ever invade a nuclear-armed Russia ... which means that NATO is not an existential threat to Russia.