Actually there is a difference. Congress cannot define citizenship. If Congress could define citizenship, they could enact a law that prevents a particular person or persons from being a citizen or NBC. They could decide who they want are NBCs and who aren’t. They could say only the political elites are NBCs and everyone else is not as they could enact a law and it would be constitutional according to your BS theory.
“Congress cannot define citizenship.”
Yes, they can. The Constitution says so explicitly. See Section 5 of the 14th Amendment.
” If Congress could define citizenship, they could enact a law that prevents a particular person or persons from being a citizen or NBC.”
No, they could not because the law has to be in place when the person is born. Otherwise it is forbidden as an “ex post facto” law.
“They could decide who they want are NBCs and who aren’t. “
That is correct. That is the power of Congress and the President signing bills.
The Founders expected the voters to pay attention and elect good people.