The elected office of sheriff, being a law enforcement office, can push back at the county level to overreaching state government, in a similar way to how state government through states' rights can push back against an encroaching federal government. It's a power of government that is closer to the people and more accountable to them, theoretically. Not to say it can't be abused but it can also serve a valuable role in checks and balances. Look up the principle of the Lesser Magistrate.
Sheriffs can push back but how often they do? Many sheriffs in the US are strongly aligned with Trump making it very difficult to see how they will push back against him. It’s more likely that they will push back against the state governors who are pushing back against the federal government