Prior to 1997, there was no interleague play. Whether a team won a division, or pennant prior to 1969, depended on what they did within league, and particularly, within the division. From 1995-1997, division record was not as important with the wild card, but all games were still played within the league. Because of that, the point could be made about the New York Mets influence in the AL East race.
The Mets sit at 73-86 waiting for the next three games to be over, but not possibly as much as their opponent, the Miami Marlins. The Marlins have totally quit and can lose as many as 95 games this season. The Yankees and Orioles currently have 92-67 records, while the Rays are 88-71, 4 games back. The Yankees beat the Mets this season 5 out of six, while the Orioles and Rays lost all three games against the Mets. The Yankees are 87-66 against the rest of their schedule while the Orioles are 92-64 and Rays are 88-68. Take the Mets out of the equation and the Orioles would be on track to win the AL East division. Who said the Mets couldn't determine a pennant race? They certainly did not determine their own, making it easy as anything for the Nationals and Braves to pile up easy wins. It is safe to say they may have influenced the AL East race more than the NL East.