In 1900, California is a middling population large state with a population under a million, and it took New Deal infrastructure projects to change that.
Utah is even less relevant.
See, by pointing out the issues with each individual area leaving the Union, you're missing my point. If the CSA leaves, then the option is on the table for any state to leave. Now, I do see people's point about states not wanting to fight a violent Civil War before they leave, but at the same time if the USA recognizes the CSA as a nation, and has better relations with it due to economic ties, secession could be seen as an opportunity for a state that is having a dispute with the Federal government to find a way out. Sure, California may not be able to secede in 1900, but what about 1920? What about Vermont? New England? Kentucky? Alaska? And so on and so forth with every state. While secession may be looked down upon after the Civil War, if we look 70 years later, when Socialists and fascists are radicalizing world, and American, politics, secession could again come to be used. It doesn't even need to have radical politics, however. If Vermont has a disagreement with the Federal government, perhaps they may think they could do it better on their own.