Xboxic has some details on the growth of SEGA over the last while.
Basically rather than trying to develop their own US groups, SEGA has bought two development groups, Sports Interactive, makers of Football Manager, and Secret Level, makers of Star Wars Starfighter.
“In recent years, SEGA has rebalanced its development strategy to be more Western focused,” said Naoya Tsurumi, CEO, SEGA of America and SEGA Europe. “On the heels of our first successful studio acquisition with The Creative Assembly, the addition of this development powerhouse further moves SEGA toward its goal of becoming a leading next-generation publisher.”