Most of the oxygen your car uses to burn today's gas comes from the atmosphere already (if your gas has ethanol added, the ethanol also provides some oxygen). CO is much less abundant though so getting it concentrated enough without having nitrogen contamination present could be an expensive technical problem that confines production to large factories as opposed to consumers being able to have their own fuel generators. You sure don't want a bunch of contaminating ammonia in your gas.

You wouldn't use any arable land, you just have a molecular biologist stick the gene into E coli and then mass produce it in a giant tank. Or some variant of that process depending on how fussy the enzyme is (apparently it is fairly fussy but it would be produced using this sort of technique, not by isolating it from plants).

Another category of states includes states like Pennsylvania which do not collect use tax through income tax forms, but the income tax packets they mail you contain warnings that you are required to file separate use tax forms (which, of course, nobody does).