Wikipedia has a convenient page listing the 34 sub-.300 winning percentages posted by MLB teams from the 1870s to the present. Here are a few observations gleaned from that list.
The only sub-.235% teams played before 1900: 5 of them.
There have been 20 sub-.300% teams from 1900 onward, versus 14 before 1900. 16 of those 20 teams were in the Northeast (that is, from D.C. to Boston and west to Pittsburgh).
Eight of the 34 teams have been editions of the Philadelphia Phillies or Philadelphia A’s. The St. Louis Browns (3) are the only team west of the Mississippi River on the list.
Three of the 34 teams played after the end of World War II; 3 played during WWII (all of them Phillies teams), and 4 played during the ’30s. The Phillies had 5 seasons from 1938-1945 of sub-.300 records. In those 5 seasons, they cumulatively went 221-539, for a .291 winning percentage. I don’t know the franchise’s history in detail, but it sounds like it suffered from malfeasance or severe incompetence during those years. All that losing explains the fervor and exhilaration that surrounded their pennant-winning Whiz Kids team in 1950.
Finally: in light of the recent scarcity of teams losing more than 105 games in a season-even the 2013 Astros only lost 111 games-the fact of the 2003 Tigers going 43-119 (.265%) is almost inexplicable.