Which species of bee do you mean? Theres a significantly smaller number of native bees in Canada, only 800 separate species vs America's 4,000. This is mainly down to the variety of local fauna that supports them and the specialisation that the species undertake.
Interestingly Apis mellifera - the honey bee isn't native to north America, it was imported to the the east coast of North America in 1622 with European settlers, it however too a further 231 years for the honey bee reached the west coast.