i think in marvel universe, there are 2 types of superhumans.
those who are born with mutant abilities, and those who are born
normal, but due to later events in their lives, they gained
superhuman abilities, like spiderman.
captain america went through some experiments which gave him added
strength, speed, agility, stamina etc. so i guess he's considered
superhero ba, that experiment also gave the black cat her
powers.