Complex sentence: After Hugo Chávez was first elected President of Venezuela by a landslide in 1998, the South American country began to reassert sovereignty over its oil reserves, which challenged the comfortable position held by U.S. economic interests for the better part of a century.
Split into simpler sentences: After Hugo Chávez was first elected President of Venezuela by a landslide in 1998, the South American country began to reassert sovereignty over its oil reserves. This action challenged the comfortable position held by U.S. economic interests for the better part of a century.