Ducati dude, US vs Euro refers to the BB (bottom bracket) shell diameter and configuration.
US BB shells are much larger diameter and were developed on bikes such as beach cruisers which used a one piece crank (the bigger diameter is required to get the OPC in at an angle). The bigger BB shell also provided a bigger welding surface.
Most older BMX's (and new cheaper ones) use this bigger BB shell except mini bikes. the BB cups on US shells usually just press in whereas the euro BB shells are normally threaded.
and no, you can't stick a 1098 motor in a BMX!
