With respect to the FAA, they don't care about the semantics (DUI, DWI, Reduced Reckless, Administrative Action, etc)...they just want to know did you get arrested and/or convicted for anything related to driving under the influence of something.

One incident is not a medical disqualifier in and of itself, but may trigger an FAA evaluation to ensure that you do not have an addiction problem. Other than that, you should be fine with the FAA.

As for the airlines, two possible problems...

1. Like NoyGonnaDoIt said, if you cannot enter Canada, you will not be able to get a job at MOST airlines. A small turbo-prop-only commuter might be an exception if they don't go north. I know a DUI will keep you out of Canada for at least 5 years, after which you can get a waiver. I don't know about a DUI reduced to something else. I suspect that you might be OK with Canada, but I also suspect the airlines won't know for sure and will probably just not hire you to be on the safe side. You may be able to head that off at the pass...my recomendadtion would be to do the research to find out what Canada's policy is in your specific case. Get the answer in writing, on letterhead from the Canadian embassy/consulate, or from an attorney if the Canuks won't provide it. Then you can go to an interview and assure them that you can fly to Canada. Do not leave any doubts about this, or they will simply move on to the next applicant.

2. You have a recent DUI, even though it was called something else. Airlines will usually hire such folks only after they run out of applicants who do not have such a history. They will be wary of your judgement and restraint.

Things in your favor:

The charge was reduced to something less ominous, which makes it easier to rationalize.

You were young when it happened. If you don't have ANY other blackmarks, you will get over this as time passes. Unfortunately 2-3 years is probably not enough time 5-7 (or more) is probably what they want to see before employers can really disregard the incident.

Also it sounds like you are not even a private pilot? That's good, if you were already a commercial pilots (even a 250-hour 172 captain) there is an expectation that you should have known better. Non-pilots are not held to the same standards as pilots.