The approximately $700 nonstop airfare from SEA-LHR on Northwest is still available for June departures. I think this is the cheapest US possibility to Europe in that time period.

You’d have to decide whether it was worth it to use AA to get to Seattle, and then take this flight, and then either take another flight or the Eurostar to Paris.

Because of possible delays with planes and trains, I’d recommend a night in London each way.

I’d expect the train or flight between London and Paris to cost about $200 roundtrip.

I would also take a serious look at possibilities from Chicago, as it may be less hassle to get to Chicago and take a cheap flight, then it would be to do the above. For example, you could take Air Indian nonstop to Frankfurt for $901, and then you can get cheap train tickets for 39 Euros each-way to Paris (per person). Again, I’d recommend a night in Frankfurt each way.

Yikes—I just checked SGF to every European gateway airport (thanks to ITA!)—and fares seem artificially high to me. Granted, Springfield MO is not a huge airport, but all fares to all destinations—even ones that are cheaper from most other cities—seem clustered in the high 11s to 1200s rt—even with late May departure. (One exception: SGF-BHX if dep. May 25 $751). A quick run of consolidators from Bookingbuddy.com didn’t find anything significantly better.

I can only tell you what I’d do if it were me in your situation—and I don’t always choose the perfect path, in hindsight! But I would…
1. Think long and hard about burning 20,000 miles unless I knew for sure I’ve got seats on flights that work with my much cheaper international connection
2. Wait. Not too long, but if I have flexibility with dates, then give it at least another month before having serious concern again. The next 30 days might* turn up something better—especially if you’re outbound before mid-June, and even better if outbound before June 1. (*might=I don’t have a crystal ball, past airline sale trends are no guarantee of future sale occurances)
3. Sign up for fare alerts at [url=http://www.farecompare.com/search/year-homepage.html?destination=Paris-All%20Airports,%20FR%20(PAR)&p=1&s=r&t=r&departure=SGF&type=homepage]FareCompare[/url]

Thanks Don and Traveler!! Okay Don, I’ll wait a little longer but man is it nerve racking[&:]!!

Well Don there’s plenty of flights for the airmiles to NYC to catch the international flight there so that’s not a problem.