Well I'm a Geography major and have taken a shit ton of treehugger courses. As far as I know the Ozone has nothing to do with our cars. It is affected by chlorofluorocarbons which came from refrigerants, solvents, and foam blowing agents. Some of which don't use CFC anymore and its the chlorine that reaches the atmoshere that damages the ozone. Global warming is a totally differant problem caused by extra greenhouse gases in the atmoshere trapping more heat then normal. This is all part of the Carbon cycle and is totally normal. The more CO2 in the air the hotter it gets the more rain we have. The more rain the less CO2 that is in the atmoshere and the colder it will get. Basically rain takes the stuff out of the air and into the sea were it goes to the bottom and gets pushed into the Earth threw plate techtonics. Plants also can absorb a ton. Then Volcanos throw the CO2 back into the air. Now anyone with common sense knows that we are adding extra CO2( and other gases) into the atmoshere which in my opinion is just increasing the Earths natural cycle. The fear most have is if there is a tipping point from which the natural cycle is broken and the Earth doesnt recover from it. Now I do beleive many are blowing it out of portion in order to make money, get elected, or whatever. Even if the US did something other countries would do shit about it like China and India which do more harm then we do. As another person said it could lead to the EArth freezing and then we will need alot of CO@ in the atmoshere to heat us up again ..

Now this is a basic, basic answer you could write many books on everthing that is envolved

Here is some site on the ozone: epa is pretty good source..
Ozone Science: The Facts Behind the Phaseout | Ozone Layer Depletion | US EPA