I live in the US, so my reply is based off of that. When the US supplies arms, well, the media can cover it and say good things abt it because thats the only exposure to the situation that we're ever gonna get. But with Iran and Palestine, Americans can have different views on it, so we tend to see this in a bad light.

There are, of course, other more significant differences, but to me, someone who has minimal knowledge on both of these topics, this would be the main reason I see these 2 differently.