The big problem with moral capital is that there is no real international consensus: the differing reportage and pre-existing prejudices in different countries will lead to the same action being reported differently in different countries
The international consensus most widely cited is the UN. Both the US and Israel can't ignore how things are perceived and acted on there. Both these countries are mainly acting on domestic democratic pressures. There is a balancing act between these pressures and good strategy in general. The leaders of these countries at times seem to be slaves to their voting constituencies, ignoring the consequences in the UN (and various other groupings). Both their roles and positions in the world depend on preserving moral capital somewhat.
Moral capital also devalues with frightening rapidity, thanks to the world's short memory...
I would argue that for example, the holocaust and 9/11, moral capital hasn't devalued - it has been spent. Recalling the memory of the holocaust still gives Israel latent moral capital. 9/11 hasn't been forgotten by the world - the world thinks US has exhausted its moral authority.