That, yes, but more that nothing in the film is actually affected by these plot points. If the romance was absent, what would be different? Nothing. If Sam wasn't struggling to find his place, what would be different? Maybe something, but I can't tell you what.
What exactly do you mean what would be different? That's kind of like asking what would be different if Batman had never unretired himself in THE DARK KNIGHT. The differences are fairly obvious: Sam's premise would change, but the overall story premise would remain the same, as would the outcome of it.
If there was no romance there'd be no romance. Would that be a horrible thing? Well, maybe not (debatable with Megan Fox involved for many), but the romance does add at least a bit of additional heart, stakes, relevance and conflict to Sam's quest. With Mikaela involved, his decisions take on another dimension entirely, as now he has to consider her well being and feelings in his choices, a future with her, safety, etc, weighed against the bigger picture. Concretely though, with this plot, if Mikaela didn't care about Sam, she doesn't go visit him, there's literally no depth to the The Pretender showing up and it's role in Sam's life, Wheelie doesn't come into play as he did, and no one ever figures out anything about what's about to happen to the Earth, which strikes me as a bad thing.
If Sam didn't embrace his role in events, its fairly obvious that Optimus Prime would not have come back to life, and no one would stop The Fallen and the Decepticons from destroying all life on Earth. I mean, I guess we can hope someone might have stopped them, but I just don't see that happening, per what the movie shows. That seems like a pretty big change to me.
It's not like he had the option to say "I'm not playing this game any more."
Sure he did. He chose to go on with his quest.
Now, you might say that Sam didn't affect the story, but the story affected Sam. Meh. Sam said he didn't want to help, but then later decided he did want to help. There's just not much there to make that meaningful or interesting.
The story affected Sam and Sam affected the story.
It's not executed particularly well. There's not much of a struggle from Sam, he just doesn't to help or feel he can, and then something happens that makes him want to help, and feel he can. There's no uber dramatic "turning point moment" where Sam sees or experiences something that suggests he needs to be a part of the Transformers world (though his reaction to Prime sacrificing himself for him is somewhat in that vein). This is the film's major weakness, but the story elements are still there. They're not some empty framework. If you can't glean that Sam feels a responsibility to the Transformers, and as he realizes the scale of events, to the Earth itself...
You only believe he had this change of heart because the film tells you. It doesn't show you.
And again, this a weakness of the film as a whole. Telling more than showing. But what do you consider Sam actually experiencing events that involve him, realizing the scale of what he's involved in, and choosing his place in them? Is that not showing to an extent?