Calif. still determines a presumption of being under the influence of alcohol with a BAC of 0.08. Although the sentencing has gotten tougher, we have not decreased the level. And the field sobriety tests are a little tougher than walking a line and finding your nose. Just because you might not be inebriated enough to fail the tests, doesn't mean you won't get cited and lose your license. The police use those tests to weed out the VERY drunk.
Seat belts come in a variety of formats apart from the retractable belts common in Australia.
Some cars have the belt attached to the door rather than the pillar between the doors. While others have a track running along the length of the door that the belt automatically slides across when the door is opened. This can cause confusion when changing cars as the latter cars require you to open the door to automatically unbuckle wheras the former cars will strangle you if try to open the door without unbuckling. Also cars will beep at you if you don't put your seatbelt on. Most will not pull someone over on a seat belt violation but will add a costly surprise if you are pulled over for something else and are not wearing your belt.