Simplify the following text for a Grade 15 native English-speaking person.
Original: Nations making their first appearance at the Winter Olympic Games were Argentina ( first participation of a delegation coming from a country belonging to the Southern Hemisphere ) , Estonia , Germany , Japan , Lithuania , Luxembourg , Mexico , the Netherlands , and Romania .
Simplified: This was the first time many countries attended the Winter Olympic Games , including Argentina , Estonia , Germany , Japan , Lithuania , Luxembourg , Mexico , the Netherlands , and Romania .