Imagine you were having a cottage weekend with a large group of your friends, and everyone agreed to bring alcohol of different types that would be shareed amongst everyone. Everyone brings a bottle of booze or a case of beer each, but one of your friends is rich, and he says he'll bring a keg because it's no big expense for him. After a few years of this, the rich guy, who's gotten even richer, starts bringing more than just a keg; he starts bringing a selection of high priced whiskeys and tequilas, spirits of every variety, craft beer sampler packs, cases of wine, and yes, still the keg. He always insists on everyone drinking what he brings (he's proud of it and genuinely just wants you to enjoy what he's bringing) and so people eventually stop bringing their own booze unless there's some really niche drink that they know he probably won't bring.
That's NATO and the US over the past 75 years.
Except now the rich dude suddenly, out of nowhere, looks around and goes "You fucking mooches, why don't you bring your own share!".
Dafuq?