International flights often get priority if airports are having delays and you'd rather be on a flight to Paris instead of a flight to Chicago or Atlanta.

Since most European flights from the US leave in the late afternoon/evening, if you have to connect on to European flight and your previous flight gets delayed or canceled, your next option might be 24 hours away at a minimum.

But if you can get to Europe on your first leg, there a many options to travel intra-Europe, and the requirements that air carriers have in Europe to accommodate you if there is a cancellation/delay are significantly more in your favor than it is in the US.  As an example, I got delayed last summer on an itinerary going from Ireland to the US.  I ended up having to add an extra leg on the flight home and got home 3 hours later than my original flight.  Delta ended up sending me $500 of cold hard cash because of European requirements.  If the same issue would have happened in the US, Delta would have had no compensatory requirement.

if you're flying from Salt Lake there are 3 European non-stops per day (London, Paris and Amsterdam).  All 3 get you to major hubs in Europe that have many options via air, rail, bus, boat or car that can get you to your final destination.