Travel from Inverness to Dublin and on to US

Sounds like it could be scary short time. Checked bags?

https://www.dublinairport.com/at-the-airport/passenger-information/us-preclearance-facility

How long the line may be for you to go through the process is a variable that is hard to predict.

How long before the scheduled departure does your US bound airline close boarding?

about an 1 1/2 hours

How 'about' is it?

May be a good idea to explore some alternatives, just in case.

Another issue is you will be making an 'international' flight from Scotland(UK) to Ireland. Others here may have knowledge ( I do not) of what processing you have to go through to 'enter' Ireland from Scotland, before you 'exit' to board your US flight

It's going to be tight for a couple of reasons, even if your flight is right on time. First, in my (admittedly limited) experience these short-haul carriers like Loganair use a far-flung tarmac so after you land, you have to ride a shuttle bus to the terminal. It takes quite a while to unload the plane and get everyone on the bus(es) and then drive slowly across the tarmac. Then, as stated by the previous comment, you're required to go through "U.S. Preclearance" in Dublin airport before you can go to your flight's boarding gate. This is not optional.

See https://www.dublinairport.com/at-the-airport/passenger-information/us-preclearance-facility

Since you've already purchased your Dublin-US ticket, it looks like you cannot put the entire journey on one ticket, is that right? If you could put it all on one ticket, if you miss your connection due to no fault of your own the airline would be obligated to modify and put you on the next flight to your US destination. Also, having it all booked together means you can check any checked bags through to your US destination. But if you buy the two tickets separately, you'd have to retrieve your bag before going through preclearance, and you could lose the price of your Dublin-US ticket if you were to miss your connection. This latter scenario is not one I'd want to risk!

If the Inverness-Dublin-US journey can't be purchased all in one, then I'd recommend flying to Dublin on the next earlier flight, even if it means staying overnight in an airport hotel in Dublin.

This information is very helpful. Thank you

There will be next to no checks when you enter Ireland from the UK.

The time consuming part will be security and US pre-clearance at Dublin.

I would not rely on making this connection. "About 1.5 hours" is too tight for a connection where you must make the next flight.

As luck would have it, I am also coming from Scotland (though from Edinburgh) to Dublin (Stobart Air, an Aer Lingus partner), then flying home to the US (Aer Lingus) later the same day. On two different tickets. If we miss the second flight, we will die (well, not really, but we would want to die, because we would have to buy a new ticket home). I've allowed a six hour layover in Dublin. Any shorter than that and I'd be sweating it.

What you need to ask yourself is, what exactly would happen if you miss your connection? If you are on two separate tickets, then you have to buy a new ticket home (serious $$$).

Your short connection, plus the very significant negative consequences if you miss the connection, put your play waaaay beyond my comfort level. Way too risky for me. I'd fly the first leg the day before and sleep in Dublin to ensure you don't miss your long flight home.

All good advice above. As you are not travelling on a genuine connection, you need to go through passport control and baggage reclaim in Dublin, you won't be able to use the Flight Connections facility. https://www.dublinairport.com/flight-connections/self-connecting-passenger-information

Very risky. Planes can be late for many reasons. Yesterday, my flight was an hour late leaving because a flight attendant became Ill and we had to wait for a replacement.

Plus with everything that has to be done at DUB between passport control, security and preclearance, you would find the connection nerve wracking at best.