Corporal punishment is banned in many countries, such as New Zealand, Sweden, Germany, Portugal, Ukraine, Israel, Denmark, Brazil, Kenya and Congo, amongst many others. These nations don't seem to have a particular discipline problem amongst their children, so I don't see why more countries wouldn't legislate against a behaviour that is clearly not better than other discipline techniques, and is also known to have plenty of negative effects.
What is everyone else waiting for? This research reported has been consistent for over two decades — nothing is going to change through waiting, except that more children are harmed by their carers' behaviour towards them.
I didn't know it was banned in Portugal but I would say this as a portuguese and having a school aged kid, parents hit their kids a lot here. Maybe not in the middle of Continente (walmart) but at home. Not beat them to death, but spanking their butts and the likes is quite common (and between parent talks, they are even sorta 'proud' of doing so)
As far as the US goes, I wouldn't doubt that it's intertwined with our religious history. "Spare the rod, spoil the child". Still getting our child-rearing advice from bronze age shepherds.
I've seen some liveleak videos that maybe could argue that Corporal punishment being illegal is either not enforced or definitely does not work for these countries.
What is everyone else waiting for? This research reported has been consistent for over two decades — nothing is going to change through waiting, except that more children are harmed by their carers' behaviour towards them.