By vetoing a ceasefire, the United States government is supportive of killing more Palestinian civilians, especially children. Still, it is full of respect for human rights and love for humanity, and that's why it will send them humanitarian assistance sooner or later, regardless of whether it will reach them before or after death.
What is extremely at play with racist thugs these days is called rationalization; they can always find a reason for killing, never for peace built on justice. Of course, they can give you a "good" reason for the veto.
The simple question never asked in mass media: what exactly are the israel military (i.e., Israeli occupation force) and 700 thousand illegal settlers doing in the West Bank, and why is it controlling Gaza's air, water, borders, and even the number of calories that used to enter Gaza?
But if you ask the question, and you should, those racist thugs will rationalize their racist position (some of whom can be physicians and professors) and can give you a "good" reason for blatant occupation and continuous abuse of human rights as long as they are Palestinians' rights.