Why did England fail to develop a large empire at the same time as Spain and Portugal?

England (it will not be Britain until the Act of Union in 1707) just went through two very costly wars in the fourteenth and fifteenth centuries--the Hundred Years War and the Wars of the Roses, respectively.  These wars were quite expensive and took away from royal coffers.  While Spain was fighting the Moors and unifying the kingdoms of Aragon and Castille into Spain, England had to expend its resources in a longstanding war with France in which it lost its territory in Brittany and in a civil war.  Also, Spain and Portugal had more territory to draw its natural resources from and a larger population.  Spain and Portugal also had trade networks with the Italian city states which supplied most of Europe's best mariners for exploration--Columbus, while he sailed for Spain, was really Genoese.