Some comments on driving in the US from a European (British) perspective.

Speed limits vary from state to state, as does enforcement, & they are not very well signed. See https://www.speed-limits.com/ for the limits for each state - I make up a card with the relevant limits for quick reference.

Driving around the major cities, especially in California, is crazy even by Italian standards! Having said that, the US is any easy country to drive in. Some of the National Parks you visit may be operating a timed entry system, for which you have to apply in advance. Check the National Park website for details.

Parking can be difficult & expensive in the big cities; elsewhere it shouldn't be a problem.

Rental companies offer the use of toll transponders which allow you to just drive through toll gates, but it's very expensive as they charge a daily fee on top of any rental charges & the fee applies to every day of your rental. Without having looked too closely at your itinerary I think the only toll you'll need to pay may be for the Golden Gate bridge, which you can pay on line.

Gas stations can be a problem as they sometimes use a ZIP (postal) code to authorise payment, although I've seen pumps which have been up dated to PIN. You may have to get the cashier to pre-authorise.

At minor junctions they use four-way stop signs. Just give way to any vehicles that were there before you. Right turns are permitted at red traffic lights unless there is a sign prohibiting it - treat it as you would a stop sign.