There were still formerly enslaved people alive when the US joined WWII
Although slavery was abolished in 1863 in the US, black people were segregated from whites for almost a century. For instance, the US Army accepted black recruits but relegated them to separate regiments. Nevertheless, things changed during WWII when many African Americans were drafted into the military.
Many formerly enslaved people were still alive by 1941 when the US joined WWII. It stands to reason that a good number of them did not see the draft measure in a positive light. Still, many young black men voluntarily enlisted to fight.