There is no Global setting.
But you will end up wanting a table of users in your app to use for drop down lists anyways.
When you just are using the native User field, you will be unable to filter the drop down list. You will find that for some apps you only want to have the drop down list fir Managers, or technicians or some other criteria.
But there will still not be a global setting. It�s an extra Click when you create each User field.