The United Sates is not the only country in the world that allows sentencing juveniles to life without parole.
Antigua and Barbuda, Cuba, Dominica, Israel, Nigeria, Saint Vincent and the Grenadines, the Solomon Islands, Sri Lanka, Tanzania also do.
The US only allows such sentencing in the case of murder. I have no problem with a murderer getting life without parole. Even if they are juveniles. Although I would prefer that they get the death penalty instead.