What is the difference between a Euro American Spanish and mid bottom bracket?

American bottom brackets can be recognized because they have the largest bearing cups you'll find, and the crank that fits into them is a one-piece design (it's also called an Ashtabula crank). This type of BB is usually found on entry-level bicycles. To take this BB apart, you need to first remove the left pedal (turn it clockwise to remove it). Then you can easily take the American BB apart with plumber's pliers. Euro bottom brackets are the smallest and usually the lightest style of bottom bracket. You use BB tools to remove the crankarms and remove the BB cups from the frame so that you can service the bearings.

Mid bottom brackets are a press-fit design, which means you can press in and pull the bearings out with your hands. These BBs use medium-size bearings and are found typically on high-end bikes. Spanish bottom brackets were invented by a company called Fly bikes. They use the Mid bottom bracket design and reduce the size of the bearings, thus reducing weight a bit. They share the press-fit design for easy assembly/disassembly. Spanish BBs are favored by pro BMXers.