If I'm travelling United from Melbourne to San Francisco and internally within the USA by United, is there a checked baggage fee for International travellers regardless of class o

If I'm travelling United from Melbourne to San Francisco and internally within the USA by United, is there a checked baggage fee for International travellers regardless of class of travel. The United website is hopeless to understand this issue. It does not make it at all clear, I'm lead to believe that every flight I get on with a suitcase being checked it's going to cost $35, presumably UD$, can someone explain better than the United website does. Also, If flying Business class from Melbourne, does United still have or share a Lounge at Melbourne Airport that I could use.

It depends if your long haul flight is ticketed together with the domestic US flights.

If ticketed together then long haul baggage rules appy to the domestic flights.

If they're ticketed separately, then you will have to follow the conditions of the separate tickets. i.e. pay for bags if the domestic booking does not include free checked baggage.

Your ticket should clearly identify the number of free checked baggage you're allowed to take with you. If you are unsure, call United and ask for clarification with respect to your ticket. This information will be detailed in the reservation system.

if you have no status and are traveling economy, MEL-LAX-SFO on the same ticket gets one bag free, second is USD100.  weight limit is 50 lbs.  in Business it's two bags free, 70lbs each.  UA uses the Air New Zealand lounge.

if your US domestic journeys are separately arranged and ticketed, economy is USD25 for first bag and USD35 for the second--up to 50lbs each.   Domestic First still gets two free checked bags, up to 70lbs each.   Pay attention to that difference as they sometimes offer for-a-price upgrades before departure.