Actually, while it must be said there was a certain level of political will in the U.S. to intervene on behalf of England, the tipping point at which it became a politically viable option in the face of isolationist tendecies, only came once it became obvious that should England fall, the U.S. would be next on the list.

So it was certainly self-interest, rather than some pure altruist tendency that motivated U.S. efforts in the first place.

But that is as it should be. No-one expects to provide help, military or otherwise, for no return and it would be foolish in the extreme to do so. Equally painting the U.S. as being some saintly provider of selfless aid to those in need is at least as foolish.