That is very petty, and nit picky. Using the abbreviation is just habit. Do not read something into it.
Just that many people won't have a clue what you mean, presumably ca is california, but some I don't hav e aclue on.
As far as the metric system, I and most science oriented Americans, support this system as is by far better. What can we do? Industry has made the change, but it is still taught in lower grade levels.
Only metric has been taught in schools here for years - so imperial is dieing out as the older population does
Great fun with work experience kids, asking them to cut something a foot long