Connection time in Frankfurt - Sufficient?

So you are flying from somewhere in France to FRA and then on to SEA?

Is this one ticket, or is France to FRA one ticket and FRA-SEA another ticket?

If the former the airline has determined the connection is viable( and if you miss the plane its on them to get you to SEA); if the latter you are in grave danger of having buy a second FRA-SEA ticket should you arrive late.

Without knowing the ticketing arrangement, an answer to your question is not possible

It helps to know the airlines as that determines the terminals you arrive and depart from. Where in France?
If it was me, I would have taken the train from Paris to Frankfurt instead of flying as it is less hassle and probably faster when you put it all together with the coming and going, etc.

I've done connections in two opposite ends of Frankfurt with the arrival flight using a bus instead of a gate: in 1 hour. Smart? No.

Assuming a single ticket, we have made changes in Frankfurt within that time frame. Don't spend time in the Duty Free shop but the German's are pretty will organized.

For best advice we need to know the airline(s) and whether you are flying on one ticket or two.

If you are flying Condor to Seattle, there is an extra document check to enter the departure area at the gate, and then you board a bus to board the plane. This takes extra time.

If it was me, I'd be very nervous! What airport in France are you flying in from? What time of day?

Second what Lola said. Condor was chaos last week at Frankfurt. We got off a flight from Athens. (And keep in mind we've transited through Frankfurt two other trips.) It took us about 15 minutes to figure out where the Condor flight to Seattle was leaving from. It then took us about 20 minutes to walk there - it was a long way and it was not as well signed as I remember. We finally found the Condor gate and it was down the stairs from the rest of the surrounding gates and there was a line of 100 or 150 people all waiting to walk into the waiting area for the flight. It was easily an hour-long line. And we had to do it even though we had checked in online and had boarding passes.

Then, we were let into an area to wait for the bus out to the plane. They were short on buses on our departure day and could only have one 55-rider bus. That bus had to go back and forth from the gate to the plane numerous times. It took forever.

Note that if you are flying Condor, you must be ticked and checked in and at the gate 60 minutes before departure: https://www.condor.com/us/flight-preparation/check-in/check-in-at-the-airport.jsp

We are flying from France to Seattle in October and an itinerary we
are considering includes a 1hr 25min stop/change of planes in
Frankfurt (FRA). We will be flying direct to Seattle from there.

Is this connection time sufficient?

No. Your inbound flight from your French airport could be delayed. I would allow 2 1/2 - 3 hours for one itinerary (meaning one ticket from France to Seattle via Frankfurt) and 4 hours if you purchase 2 separate tickets.

This would be single ticket, operated by Air Canada. Seattle-Marseille-Seattle. Return flight includes a 1hr 25min change of planes in FRA. That's the only stop on our return flight.

I just did this with the exact same connection time, 2 weeks ago. We had more than enough time and signs were clearly marked. In fact, I laughed knowing I was nervous about the connection time and we had at least 45 minutes to wait just for them to start boarding. Germans are extremely efficient! So easy as long as you are on one ticket.

This would be single ticket, operated by Air Canada.
Seattle-Marseille-Seattle. Return flight includes a 1hr 25min change
of planes in FRA. That's the only stop on our return flight.

What is the plan if you miss the connection?

Are there more flights to SEA on Air Canada? I didn't realize Air Canada has direct flights between FRA and SEA with no stops at a Canadian hub or is this code-shared as Air Canada but the airline is Lufthansa? If so, see how many Lufthansa flights go to SEA after the one to which you are considering. If you miss that connection, you'll want to have as many opportunities as possible to get seats on subsequent flights to SEA that aren't sold out and thus have available seating.

Thanks all for your responses and advice. We've booked an entirely different set of flights with great connections.

What did you book?

Norwegian Air SEA-LGW-SEA and EasyJet LGW-MRS-LGW. With extra time in London on both ends to see some of the city.