However, the spirit of it is that you would be involved as an observer, and being involved as an observer is still more involved than I would have wanted to become.
In this case what you are saying really is "I would never have wanted to have versed into Pearl Harbor at that time and place." Sorry, John, that's the way the game goes. I'm sure that Eric would never have wanted to verse into The Web; I know that Tristan never wanted to verse into Cask of Amontilado, a world that scarred him for a long time; I'm sure that Kyler would argue he never wanted to verse into Why Spy despite the fact that that's where he got his big sister Mariska; I don't think I wanted to verse into Vampire Chicago and face magic-using vampires intent on conquering the world. You are dealt the world you are dealt, and you make what you choose of it. I could have walked away from Chicago and said, "Let the Vampires have it; after all, everyone knows it's the most corrupt city in the United States, and the Horta administration can't be worse than the Daley one was. It's one set of bloodsuckers or another, and that's not my business." Kyler could have said, "So kill me, then," and he could have gone on the run and dealt with trained assassins coming after him. Tristan--well, Tristan couldn't have done much of anything, as he was pretty clueless the whole time and didn't know what was happening until the guy came after him with a gun and failed to kill him. The point is, you land in a world and you decide what to do there. You are never less involved than present and observing, and if you're going to say that that's "too involved" then you're out of luck.
I could think of plenty of ways an observer could have a meaningful level of involvement without warning them of the attack. Suppose whilst he was in there giving his cover story, he charmed the secretary into going on a date with him. She calls in sick to work the day of the attack, and as such, isn't killed. You'd say that wasn't meaningful involvement. The secretary would disagree. What constitutes "Meaningful Involvement"?
Sure, I can think of a lot of ways you can become involved, but when you said "he charmed the secretary into going on a date with him" you crossed the line from non-involvement to involvement.
There was an episode of Star Trek Next Generation in which a guy arrived in a time machine and claimed that he was there strictly to observe the events surrounding a major moment in history that was about to happen. It happens that he wasn't; he was there in a stolen time machine intending to steal technology from his own future so he could invent it in his own time in the past. Certainly telling them he was there to observe created the sense that something important was about to happen, and probably impacted the way things were handled--but who says you have to tell anyone you're an observer? You're here by mistake, you're here by accident. Or tell them you're a spy and let them execute you. Or you're from No Such Agency, checking base security, and congratulations on how well you did (and of course no one is going to confirm your identity--what's the point of having a covert organization if people know it exists?).
Is it meaningful involvement for the secretary to live? For the secretary it is; for the United States involvement in World War II it probably isn't, and that's the thing that was worrying you, right? You don't care whether the secretary lives or dies; you care whether the United States enters World War II.
What about Final Countdown? Was it meaningful involvement for the Nimitz to cruise the waters near Pearl Harbor? To shoot down a Japanese plane? To pick up and lose a United States Senator? To leave parts of a helicopter plus one engineer stranded in the past? Probably all of those things were "meaningful involvement" to someone on some level; but none of them mattered to the critical issue, which was whether the Japanese attack on Pearl Harbor resulted in the entry of the United States into the war.
So "meaningful involvement" is a matter of perspective; but from no perspective is strict non-involved observation "meaningful involvement", because it does not include going on a date with the secretary (involved) or answering questions about the future (involved).
"What's the date today? Really? Boy, am I lost--I was supposed to wind up at the Cuban Missile Crisis in 1962. What, this isn't Cuba, either? I'm going to have to get that machine fixed. Sorry--temporal prime directive, not allowed to tell you anything about the future. Look, kill me or let me go, it's all the same to me, I'm in the wrong place anyway."
That's non-involvement.
"I don't know how I got here. I must have been drugged or something. That stuff on the beach? No clue, I just woke up in the back of that strange vehicle. Last thing I remember--no, that is the last thing I remember, waking up in that vehicle, stumbling out, and being picked up by your MP. Do you think I have a family somewhere? Do you think they're worried about me? I wonder who I am."
That's non-involvement.
If you're going to make a lot of noise about not wanting to be involved, then don't be involved. But if you're going to say that simply being somewhere where you can observe is being involved, quit the game now, because you can't not be anywhere, and I'm not going to send you places where there's nothing interesting happening.
--M. J. Young