Frankfurt Connection time for International flight

You don't mention if you're buying that as two separate tickets or one. Condor will sell you the entire thing - that way you're on one ticket, not two. Just price it right on the Condor website from Brussels to Seattle. And you'll surely get a range of opinions, but I don't like connections that are short, although on a single ticket at least you're protected. Condor would be obligated to get you home - but be aware they only fly the route once a day so if you miss a flight, you're staying in Frankfurt for a day.

I like 3 hours in Frankfurt as I'd rather have time to sit and relax vs. a run though an airport.

And one other thing - I love Condor and use them regularly. However, I am not purchasing a ticket from them right now for my upcoming trip due to uncertainty about their financial viability. Condor survived the Thomas Cook disintegration and was granted a 6 month bridge loan at the end of September. So what happens in March 2020? I don't know. Lufthansa might take them over. But it's all a little unclear right now. https://onemileatatime.com/condor-airlines-future/

I am guessing you are leaving the Schengen zone and will need to go through exit immigration in Frankfurt and that the two flights are not connected -- single ticket. If that is the case, NO !!! Add at least another hour since the downside risk for missing your international flight is very expensive new ticket.

I like 3 hours, too, especially for a transfer onto a transatlantic flight if there are no other flights out that day.

We have made a connection (arrive from Munich; depart for SFO) in an hour. That included having our passports stamped. Yes, we moved very quickly down the concourse, but we arrived at the departing flight with time to spare. I wouldn't say it was my favorite connection, but that was 1 hour. It seems to me 1 hour and 45 minutes should be fine.

Assuming you don’t have to collect and re check bags, that should be barely enough time, if your flight arrives on time. In September we got rebooked on a flight from Madrid that went through Frankfurt. Time between flights was 1:40. We departed Madrid about 15 minutes late. Going through passport control took only about 10 minutes. By the time we got to the gate, boarding began within 10 minutes. Like padams, we rushed through the terminal. Fortunately, we had been in that terminal on a few previous trips and had an idea what to expect and where to go.

It is quite common to get an “estimated walking time” of 25 minutes in Frankfurt, and that’s after waiting in the “Other Passports” line to get in or out of the Schengen Zone.

check the on-time history - https://www.airportia.com/flights/lh1006/frankfurt-am-main/brussels/
The flight listed has been cancelled twice in the last month, delayed 30 minutes or more 3 times.

SandyO reports that a less than an hour FRA connection is possible but 1:30 to 1:45 would be more comfortable:
https://community.ricksteves.com/travel-forum/transportation/short-connection-time-in-frankfurt-lessons-learned

No don't do it. We have found ourselves in the same dilemma . Lufthansa seems to think its ok but you need more time. What if the flight is late even a few minutes will make a huge difference. We got stuck Amsterdam/Frankfurt diverted us to Munich /Boston and every single plane was late. They actually took us of the runway and drove us to customs because we were flying to the usa in Munich because the flight was late as well. A nightmare Plus the international flight while still on runway will close its doors and will not let you in even though the plane is still there for like 30 minutes . Just thinking about it makes me upset lol

Susanne, your post is very hard to understand. Where did you get stuck? Frankfurt or Amsterdam? And diverted to where? I'd certainly hope the doors are closed before the plane gets to the runway!