The non-US members of NATO combined are larger economically, demographically and geographically than the US is. If they all pulled their weight NATO would have (slightly) more contribution from non-US countries than from the US.

The non-US members all have different views that must reach a consensus before any action which is precisely where the machine grinds to a halt. Which means a consensus is rarely reached. Contrasting that to the US which can bring all of its might with the whims of one leader and possible brow beating of congress to agree.

In this way, NATO/UN is interchangeable from the US point of view.

> If they all pulled their weight

This hypothetical doesn't advance the original claim. Sweden might punch well above its weight. But that hardly matters in absolute terms.