Which DSLR camera brand famous and popular in U.S.A or Europe? 1. Canon 2. Nikon?

Canon is the most popular worldwide while Nikon comes in next. The industry standard is Hasselblad but rest be assured that all dSLR cameras are good no matter what brand they have.

People with no axe to grind take the oldest SLR manufacturer in Japan - Pentax - over either. ANY Pentax DSLR offers autofocus with ANY Pentax AF lens (sorry Nikon), all Pentax DSLRs meter with legacy lenses (even M42 screw mount with an adapter), and all Pentax DSLRs are fitted with pentaprism viewfinders which offer 100% coverage.

Anyone who can't see beyond Canon and Nikon shouldn't be allowed within 50 feet of a decent camera.