Because of the Electoral College, illegally-cast votes stay within state lines. Another reason why we need to keep the Electoral College.
Not sure that is correct, but not in a position at the moment to argue the point. Would you please elaborate?
At a minimum, it would seem to me illegal voting within a state could well influence whether that state sends D's or R's to the federal government.
At the presidential level a state's electors are equal to its number of reps - with the number of reps a function of population, arguably whether that pop is legal or not.