We're planning a trip to Cambodia sometime next year. Probably during rainy season as it's cooler then. Anyway, as to break up the overall fly time, my wife wants to add another destination for a few days. Lots of options. My wife mentioned Italy, but I'm not so sure. I've heard, both, good and bad, So, if it were you, where might you plan said destination? Thanks in advance for any input you may share.
You should minimize flight connections. Find out where you can fly direct to Cambodia and choose that place. Depeneds which way you are going there. I know Finland is the "gateway to Asia". I'd probably personally avoid Europe. Depending on how long, I'd say Singapore or Hong Kong.
Also, it appears you need a Visa to enter Cambodia. For simplicity sake, I would probably recommend just going there direct and back. Some flights may have "tourist layovers", I know flying to Manila, you can do a one day layover in Korea and there's a special tour.
Thailand or Vietnam....both have better food than Cambodia...and fewer land mines. Vietnam is more expensive than all three...also cleaner. Hong Kong is crowded, noisey, no night life...just shopping and food...but the food in Hong Kong is worth the trip alone. Hong Kong is less friendly than the other 3 countries....Laos is probably the cheapest...I've never been there but it's like northern Cambodia or Northern Thailand....Hmong people.
If you want to break up the flight from the east coast...stop in Morrocco on the way the best time to go to Cambodia would be dead of winter here...rainy season sucks in the subtropics..you'll never dry out...just steam away when the sun peaks out.
Cambodia and Italy are pretty different experiences but both are great. Cambodia is great. I went to Siem Reap to see the Angkor Watts in 2018 to fulfill a buck list item. The Angkor Watts are amazing and require at least one full day. You could really geek out and spend a week on them but after a day it all starts looking the same and you have seen the highlights. The Watts themselves are cities and there are lots of them so you need a car to get around to them all, we hired a personal guide and a driver for $35 for the whole day. They even packed snacks, beer and water. Things are crazy cheap also, full epic meals for less than $10 total for the whole table. Our hotel was amazing for somewhere around $40 a day. Thing about Siem Reap is that it is small though. You will run out of things to do after three or four days, and honestly I cant think of many other places in Cambodia worth spending much time in. I would make this part of a great tour of the area, you can easily catch a really cheap regional flight from Siem Reap to Bangkok, Chang Mai, Koh Samui, Phuket and more. Personally, I would add this to a Thai beach vacation. Italy is a whole other story, I could go on and on and on about there. Just did Florence and Naples and have been to Rome and Venice a few times. They are all amazing and very different. If you have never been to Italy then you have to check it out. A few of my other top suggestions are Cartagena, Colombia. It is a romantic city and very fun and affordable. Also a lot closer to home. Buenos Aires and Icguazu Falls are an epic trip combo also, but probably not viable if your trying to group it with the Cambodia travel.
My wife has been to Cambodia three times. I've never been. My wife has gone in the past to help support our close friend, who, for many years, has maintained a ministry there which equips teen girls to gain skills and acumen which goes far to help them escape the sex traffic business that's rampant over there.