The answer here is complex and I doubt you actually want depth. But to clarify your statement, each COUNTY within a state manages their own election. California is also one of the biggest states in the country and the population of some counties dwarf the size of entire U.S. states. So the first answer is, it's a complex operation WITHOUT any obstruction attempts, but we live in this reality, and gop obstruction is rampant and regular at this point.

An epicenter for election threats and disinformation in California is Shasta County. It will probably take some time for them to dissect all of the subtle ways that this fucked their process, but late in the election cycle, their garbage county supervisors hired a lawyer with no election admin experience to replace the departing competent person who had run elections. Here's an account from a local paper wrt some of what is allowed to go on in that country:

"CalMatters’ Sergio Olmos visited last week and reports that the presence of self-appointed election observers has led some elections workers to quit. The observers spend their days at the county’s registrar of voters office on the lookout for any misdeeds related to voter fraud. Though voters are legally allowed to enter the office to observe the election process, staffers report that the observers have been following workers into their breakroom and attempting to open doors to see inside their offices. Their intensity pushed Tanner Johnson to quit after working as an account clerk for more than a year. He says that 10 of the registrar’s 21 employees have also left. *Johnson: “They want to catch us in a lie, so they’ll try to trick you into saying something. A lot of times they’ll be secretly videotaping you or recording you. … I make $19.64 an hour. I’m not going to be a martyr for $19.60 an hour.”

So that kind of ceaseless, cowardly, undemocratic intimidation has been long present. It leads to stressed, threatened volunteer temporary workers who don't get paid enough to deal with that bullshit so if nothing else, they naturally slow down. It also leads to high turnover for those positions from the fear/stress, which means people are more likely to be undertrained or frankly, lower quality job candidates as you've already cleared out the "starting lineup and the bench" in some cases and then you're just desperate for any bodies off the street - including some of these pieces of shit themselves that learn the systems so they can purposefully volunteer and obstruct from the inside work challenges to ballots that are false, but require time in a process for people to then come and do a focused verification process to reclear as flagged ballot - like the tidbit that was caught streaming those "sample" verification ballots and then immediately challenging the validity of their elections process because they didn't have those ballots (that he obviously stole, on camera)

At the larger systemic level, they've challenged valid systems meant to expedite voting and vote processing so much and for so long now, that you're left (intentionally by these GOP efforts) with a patchwork of disjointed, disconnected and overly careful processing flows that move especially slow to attempt to satisfy their never meaningfully justified "voter fraud" bullshit - claims they are now, suddenly silent about, just like with those "caravans!!!" at the border

I could write you an essay, but I doubt you actually, truly give a shit.