BS; no other states prohibit such labeling. How many products have some sort of California warning on them already, regardless of where they're being sold? Hell, a lot of stuff already comes with French labeling and instructions, even in Texas, so obviously they're not overly concerned with area-specific labels.
Two things: California is a big enough market to cause every manufacturer to change their labeling for everywhere. Oregon isn't.
Second, the French thing is so that manufacturers can sell both here and in Canada at once. Canada's market is about the size of Cali's (both have ~35+million people, though Cali's GDP is about 2x that of Canada). Again, Oregon isn't going to be enough to convince every single manufacturer in every other state to label ALL of its food that way.