BigQuery - Concatenate multiple rows and columns into a single row

Below is for BigQuery Standard SQL

#standardSQL
SELECT id, STRING_AGG(CONCAT(name, ' ' , country)) text 
FROM `project.dataset.table`
GROUP BY id   

You can test, play with above using sample data from your question as in example below

#standardSQL
WITH `project.dataset.table` AS (
  SELECT 1 id, 'John' name, 'Usa' country UNION ALL
  SELECT 1, 'Tom', 'Canada' UNION ALL
  SELECT 1, 'Bob', 'Italy' UNION ALL
  SELECT 2, 'Jack', 'China' UNION ALL
  SELECT 2, 'Tim', 'USA' 
)
SELECT id, STRING_AGG(CONCAT(name, ' ' , country)) text 
FROM `project.dataset.table`
GROUP BY id   

with output

Row id  text     
1   1   John Usa,Tom Canada,Bob Italy    
2   2   Jack China,Tim USA