If condition to check if all values of one list is present in another list

I need to write a if condition. It should enter the if condition only if all Nationalities in nationalities List [A,B,C] is available in separate List.

CASE 1 : If SeparateList contains[A,B,C,D,E] and if nationalities List contains [A,B,C], all values in nationalities List is avialable in SeparateList. Therefore it should satisfy 'if' condition.

CASE 2 :If SeparateList contains[A,C,D,E] and if nationalities List contains [A,B,C], B value in nationalities List is not avaIlable in SeparateList. Therefore it should not satisfy 'if' condition.

But currently my if condition is satisfying case 2. I think it is because of Intersect. So please suggest any ideas.

 nationalities.Add(nation.ToUpper().Trim()); //contains list of nationalities [A,B,C]
    
 if(nationalities.Intersect(separateList(bg.Nationality)).Any()) 
{
// code 
}

private List<string> separateList(string input)
        {
            return input.ToUpper().Trim().Split(',').ToList();
        }