Not as far as my limited understanding is, USA still has a Congress and a House, and the comment thread I replied was specifically about abolishing the Congress for a different solution. And as far as I know USA has not abolished the Congress, right?

Senate and House - congress is both bodies. My point was merely the additive scheme you described is how electoral college votes are allocated.

What problem does the Congress solve in the democratic process which happens elsewhere where there is no such thing?

Congress as a whole? I don't know if there's anything unique it solves. It's merely the US's compromise to balance between a monarchy and a weak federal government with little control over the coalition of states.

The big issue is that our House of Representatives stopped being proportional to the population some 90 years ago. I believe analysts suggested that a House today would have over 1000 members, as to the 435 seats today. So that only increases representation of smaller states.