The Maharal observes that all halachos of Korban Pesach pertain to unity; roasted in one piece, the bones have to be kept whole, eaten in one group, in one place, at one time etc. All these are meant to reflect that ה’ אחד – that G-d is One, and His unity is everywhere.
However, this would seem to be at odds Korbanos in general, that are meant to reflect the person bringing it. If the Korban Pesach displays Hashem’s unity, how does it relate to the people bringing it?
R’ Yehoshua Hartman explains that as a nation, we reflect the אחדות of Hashem. We have nothing to rely on but Hashem, with no fall back option. This is true across the spectrum of Judaism. In Egypt if it doesn’t rain for years, it’s not a problem, as the Nile provides water. If Israel has a poor rain season one year, there are serious shortages, and people start worrying(and when people start worrying, they start praying). We can place our faith in Hashem alone.
When the Jews said נעשה ונשמע – we will do and we will listen – what they were effectively meant was that they did not enter the equation. When Hashem asks something of us, that is all that matters.
This explains why so many Jews in history were willing to be מוסר נפש – display self-sacrifice – rather than cause a desecration of Hashem’s name. The rationale behind this is that Hashem doesn’t want something done, and if it is done, it’s removing oneself from godliness, as it is antithetical to what God wants.
In reality then, there is no contradiction. We say in Aleinu that אין עוד – which means there is no other reality other than what G-d wants. No one symbolises this more than the Jews. The Korban Pesach reflects both Hashem’s unity and the people bringing it.