Let's take this as example, my application has tables to store Country, State, City, Province. And each table has a fk to the other table.

Example

1. CountryPK will be a FK to State.
2. State PK will be a FK to City.

Assumed those data will be added from time to time. Thus, I have a default script to store all the latest data.

Default Data Script

-- * Step 1 - Create a table variable with identical structure of the actual table --
DECLARE @Country TABLE (pk INT IDENTITY(1,1) PRIMARY KEY, newPK INT, CountryCode VARCHAR(60), 
	CountryName VARCHAR(60), isNew BIT DEFAULT(0))
	
DECLARE @recIndex INT
DECLARE @recCount INT
DECLARE @newRecPK INT
DECLARE @CountryCode CHAR(3)

-- * Step 2 - Create INSERT for each default data --
INSERT INTO @Country(CountryCode, CountryName) VALUES ('UK', 'United Kingdom')
INSERT INTO @Country(CountryCode, CountryName) VALUES ('JP', 'Japan')
INSERT INTO @Country(CountryCode, CountryName) VALUES ('CN', 'China')
INSERT INTO @Country(CountryCode, CountryName) VALUES ('HK', 'Hong Kong')

-- * Step 3 - Compare Data --
SET @recIndex = 1
SET @recCount = (SELECT COUNT(*) FROM @Country)
SET @newRecPK = ISNULL((SELECT MAX(CountryPK) + 1 FROM Country),1)

WHILE @recIndex <= @recCount
	BEGIN 
		SET @CountryCode = (SELECT TOP 1 CountryCode FROM @Country WHERE pk = @recIndex)		

		IF NOT EXISTS (SELECT * FROM Country WHERE CountryCode = @CountryCode)
			BEGIN
				UPDATE @Country SET newPK = @newRecPK, isNew = 1 WHERE pk = @recIndex
				SET @newRecPK = @newRecPK + 1	
			END
		
		SET @recIndex = @recIndex + 1
	END

-- * Step 4 - Checking for State, City, Province ... --
-- ...

-- * Step 5 - Insert New Country, State, City, Province ... --
INSERT INTO Country(CountryPK, CountryCode, CountryName)
	SELECT newPK, CountryCode, CountryName FROM @Country WHERE isNew = 1

SELECT CAST(@@ROWCOUNT AS VARCHAR) + ' records added...'

Actual Table in Database

CREATE TABLE Country
	(CountryPK INT PRIMARY KEY, CountryCode CHAR(3), CountryName VARCHAR(60))

The main reason I choose to use table variable as I need a place to store the newly added PK as they will be used in the further steps of update.

Example
China is added and has a PK 3, all the states in China will have a FK 3 when inserted.

Perhaps my thought is too complicated, using a UPDATE/SELECT would be more efficient?