Simplify the following text for a Grade 9 native English-speaking person.
Original: The Soviet Union and 14 of its Eastern Bloc partners ( except Romania ) countered by boycotting the Los Angeles Olympics of 1984 , contending that they could not guarantee the safety of their athletes .
Simplified: The Soviet Union and 14 of its Eastern Bloc partners ( except Romania ) countered by missing the Los Angeles Olympics of 1984 . The countries stated that they could not guarantee the safety of their athletes .