You cannot select vehicles manually, it would be very annoying, since you would have to first select an operator, then a vehicle. The Pushback tractor is selected depending on your airplane weight and, amongst all suitable candidates, randomly, but with a livery appropriate to the airport, and with possible further limitations depending on the parking size:
What you all "US like", is not something related to the US, it's just a smaller truck that might be used with smaller airliners, you can tweak its SIM.CFG, to change the weight threshold, acting on this line, in the Simobjects\Misc\FSDT_Pushback_Small\SIM.CFG file.
condition = %(aircraftWeight)g < 175000 or %(parkingRadius)g <= 18
This line means the small pushback truck will appear if your airplane total weight is less than 175.000 lb or the parking radius is 18 meters or less.