I have updated the your input xml by adding data node name to repeating data,, its required
CREATE PROCEDURE insertdata
(@data xml)
as
begin
INSERT INTO tablename(col1,col2)
SELECT
ParamValues.ID.value('./ImpactID[1]','int') AS ImpactID,
ParamValues.ID.query('./ImpactData').value('.', 'varchar(max)') AS ImpactData
FROM @Ids.nodes('/Root/Data') as ParamValues(ID)
--FOR VALIDATING THE INPUT
--DECLARE @Ids xml
--SET @Ids ='<Root>
-- <Data>
-- <ImpactID>2</ImpactID>
-- <ImpactData>abc</ImpactData>
-- </Data>
-- <Data>
-- <ImpactID>3</ImpactID>
-- <ImpactData>xyz</ImpactData>
-- </Data>
-- </Root>'
--SELECT
--ParamValues.ID.value('./ImpactID[1]','int') AS ImpactID,
--ParamValues.ID.query('./ImpactData').value('.', 'varchar(max)') AS ImpactData
--FROM @Ids.nodes('/Root/Data') as ParamValues(ID)
Happy Coding :)