Dfyjkt

I am travelling from Vietnam to Washington via Hong Kong and San Francisco, the trip looks like this: SGN - HKG - SFO - IAD. The layover in SFO is only 1hr 25 mins, and I'm not Canadian or American, so I'll have to collect baggages, go through immigration, get to the domestic terminal, go through security and drop off the baggages. Will there be enough time? Im also flying United Airlines for the first time, and from some general opinions on the internet it seems that they are known for being occasionally late.
Edit: I booked the flight from United Airlines alone, so it's one whole ticket. Im concerned about the timing because a friend told me that I'd be on a very tight time budget to not miss the flight

It depends on a number of factors, but I'd say that the odds of you making this connection is very low. 85 minutes just isn't realistic for such a connection in most cases at SFO.

UA862 from HKG hits SFO right on peak hour. In the hour before it lands there are at least 5 other flights arriving at the same terminal, and feeding into the same immigration area - all of them widebody aircraft generally carrying 300+ people each.

If you are entering the US using the Visa Waiver Program, and if you have entered the US on the same passport in the past ~8 years, then you can use the APC kiosks instead of the normal immigration lines - but even that could be a 20-30 minute wait at that time of day.

If you have to line up in the visitor line, then it could be anywhere from 10 minutes (if your flight happens to land first of all of the other flights, which is extremely unlikely as it's scheduled to land last!) up to over an hour.

Your bags will likely not be an issue - by the time you get through immigration they will most likely already be ready. Presuming no issues, collecting your bags, going through customs, and dropping off your bags again should take no more than about 5-10 minutes, then another 5 minutes to get to security in the domestic terminal.

Security in the domestic terminal will depend on the day of the week, but at that time of day, for someone without TSA PreCheck and without 'priority', will probably take somewhere between 20-30 minutes, although could be more or less.

And then finally, United Airlines requires you to be at the gate 15 minutes before departure. If you are not there at that time, they can (and will) off-load you and give your seat to someone else - especially on flights like SFO-IAD where there is normally a long standby list. So your 85 minutes is really only 70 minutes.

I won't say that this connection is impossible - if the stars all happen to line up perfectly then it's doable. But odds are you're not going to make it. If that happens, United will put you on a later flight - but keep in mind that could be many, many hours later. There SFO-IAD flights generally run very full, so there may not be seats available until much later in the day, or even the next day.

In addition to what's mentioned in the other answer, there is one extremely important thing the airline will do to help: if you miss the connecting flight due to late arrival and/or customs delays, they will put you on a later one. (Note this applies only because you have booked the flights on a single ticket.) SFO and IAD are both United Airlines hubs, and as of this writing, United has 9 nonstop flights per day on that route, with many more connecting itineraries possible. So if you miss your planned flight, you probably won't have to wait too long for another one.

Generally, that is enough time; 95% you will make it easily.

However, there could always be a snafu on the day, but even having 3 hours doesn't securely protect you against that.

If you booked in on one ticket, the airline will help you if needed, like pulling you to the front of the line, driving you over through back-corridors, or have the connection flight wait - they have an interest in you making it too; and probably half the plane are non-americans with a connection. Note that you do not have to carry your baggage over; you drop it right behind customs back to their agents - you can only carry it 100 yards, from belt through customs to another belt.

Airlines have a minimum connection time for each airport, and they are not selling tickets with less space between flights. They typically know what they are doing, so if your paperwork is valid, you can relax.