The Absolut Haggadah (2007 edition) asks an obvious question. (By the way, you can download the Absolut Haggadah here. And see here for my short review and introduction.)
What do we mean that Dayyenu had God not split the Red Sea for us? This would have left us on the shore to be slaughtered by the Egyptians! Click on the image to see a larger screenshot.
I think that there are in fact two answers to it. Firstly, undermine the question. This is not about repercussions of God's actions or repercussions had He not acted. Rather, it is about emphasizing how many miracles Hashem did for us in the process of the Exodus. This is underscored by the fact that it continues by reiterating all these miracles immediately thereafter, without the dayenus, but with an introduction of Al Achas Kama veChama Tovah Kefulah emeChupeles laMakom Alenu. We are not meant to pause at this point and say, "this would have been enough," but rather, this miracle so far is more than we deserve.
Perhaps one can read Dayenu, it would have been sufficient cause for us to give praise.
Related, Kama Maalos Tovos laMakom Aleinu, introducing Dayenu, is quite likely not a question but rather an expression that there are so many.
My second answer buys into the premise of the question. "Had God given us their money (presumably when we 'borrowed' from the Egyptians in Egypt, rather than the spoils at the site of the shore of the Red Sea) and not split the Sea for us, it would have been enough."
But would that not leave us to be stranded on the side of the Reed Sea? Absolutely not! We would not have been at the shore of the Reed Sea to begin with! The only reason we were there in the first place was so that God would split the Sea, drown the Egyptians, etc.. This is not frummie talk or apologetics, but rather simple peshat in Chumash! Let us examine Shemot 14:
We could have gone directly into the midbar, not made it look like the wilderness had shut us in, and proceeded directly to Har Sinai.
Perhaps something to include in next years' edition of the Haggadah.