Complex sentence: Whelen Motorsports is partnered with NASCAR and sponsors, promotes, and produces the NASCAR Whelen All-American Series in which more than 10,000 drivers compete for championship at 49 NASCAR-sanctioned short tracks within the United States and Canada.
Split into simpler sentences: Whelen Motorsports is partnered with NASCAR and sponsors, promotes, and produces the NASCAR Whelen All-American Series. In this series, more than 10,000 drivers compete for championship at 49 NASCAR-sanctioned short tracks within the United States and Canada.