SQL query in Oracle to sum up values from an alias column

In Oracle I would like to make a SELECT statement combined with UNION ALL to count all rows in some tables (second column) and assign a description to each row (first column). Below is what I actually have and the result.

SELECT 'Amsterdam' AS city, count(*) AS amount FROM A
UNION ALL
SELECT 'Berlin' AS city, count(*) AS amount FROM B
UNION ALL
SELECT ALL 'California' AS city, count(*) AS amount FROM C;

I would also like to add to the result last row with TOTAL as CITY and 9 (sum of all values in AMOUNT column) as AMOUNT. Below is the visualization.

I struggle with it because I can't find a way to make another operation (SUM in this case) on a column that doesn't exist (CITY), because it is produced by my query. This is what I tried to do, but I get ORA-00942: table or view does not exist

SELECT city, amount 
FROM
    (SELECT 'Amsterdam' AS city, count(*) AS amount FROM A
     UNION ALL
     SELECT 'Berlin' AS city, count(*) AS amount FROM B
     UNION ALL
     SELECT ALL 'California' AS city, count(*) AS amount FROM C) t
UNION ALL
SELECT 'TOTAL' AS city, SUM(t.amount) AS amount FROM t;

I will be thankful for any help.

How about rollup?

SQL> with temp as
  2  -- this is your current query
  3  (
  4  SELECT 'Amsterdam' AS city, count(*) AS amount FROM A
  5  UNION ALL
  6  SELECT 'Berlin' AS city, count(*) AS amount FROM B
  7  UNION ALL
  8  SELECT ALL 'California' AS city, count(*) AS amount FROM C
  9  )
 10  -- your current query ends here
 11  select
 12    case when grouping_id(city) = 1 then 'Total' else city end as city,
 13    sum(amount) amount
 14  from temp
 15  group by rollup(city);

CITY           AMOUNT
---------- ----------
Amsterdam           3
Berlin              2
California          4
Total               9

SQL>

Or, the way you tried:

SQL> with temp as
  2  -- this is your current query
  3  (
  4  SELECT 'Amsterdam' AS city, count(*) AS amount FROM A
  5  UNION ALL
  6  SELECT 'Berlin' AS city, count(*) AS amount FROM B
  7  UNION ALL
  8  SELECT ALL 'California' AS city, count(*) AS amount FROM C
  9  )
 10  -- your current query ends here
 11  select * from temp
 12  union all
 13  select 'Total', sum(amount)
 14  from temp;

CITY           AMOUNT
---------- ----------
Amsterdam           3
Berlin              2
California          4
Total               9

SQL>