At the end of the day you could say that about most countries . NATO existed to stop the expansion of the Soviet Union. That’s it’s only reason to exist , after that America should have pulled out. George Washington warned us about these long term international agreements and he was right.
NATO also exists to keep the Germans from doing their thing. We weren’t counting on another Molotov-Ribbentrop, though. German reliance on Russian energy has been a disaster for the world.