This CSS mod seems to work:
.create-account .user-field label {
width: 190px
}
.create-account .user-field .controls {
margin-left: 200px
}
Mobile is a bit more tricky but at least on High Resolution screens, this seems to work without adjusting the width of the actual field/combobox:
.create-account .user-field label {
width: 140px
}
.create-account .user-field .controls {
margin-left: 140px
}