Achdus is the essence of our ability to recieve the Torah by Rav itamar Schwartz from a Siur about Shavuos

The achdus of Klal Yisrael is the essence of receiving the Torah. Hashem chose us as a whole, he did not chose individual. That is why we say, "Atah Bacharbanu". We thank Hashem for choosing us, not for choosing me.

If a person holds himself as a yachid( an individual) he will not be worthy of receiving the Torah. That is why "V'ahavtah L'rayicha kimocha" is a Klal gadol b'Torah.

Two things bond us together, Ahavah and Emunah (Love and Faith). A parent will always love a child even if the child misbehaves, but the same parent may not have faith that the child will always behave properly.

Hashem always loves us and he always has faith in us. The difference is that Hashem created us and he knows that we have an inner essence that is pure because Hashem created us pure. We have to have Emunah in Hashem's creation that all of Klal Yisrael have an inner and pure neshamah.

How could Hashem give us the Torah if he knew that we would sin? The answer is that the Torah was given to us as a people, it was not given to individuals. If that is the case how can we have Emunah in individuals when we know that they may sin. The answer is that we have to be able to judge everyone favorably. We have to know that there essence is pure even if there outside is not.

Hashem gave us perfection and purity as a gift on Shavuos. We took this gift and defiled it. If that is the case why are we celebrating what happened on Shavuos? We don't make a holiday on the day that the Bais Hamikdash was completed because it was destroyed after that. The answer if that the Torah remained on the same level. Even though the Luchos were destroyed the Torah remains the same. The connection that Hashem created on Shavuos remains there and every person has the ability to connect to it. Klal Yisrael has the ability to be perfect. The way that Hashem created us and choose us means that this potential exists in us today.

Because Hashem has Emunah in us we have to have Emunah in this inner potential. Even though we fell we still have the potential.

We have to know that there are times of aliyah and yeridah in our lives but we have to grow. Hashem believes in us, and we believe in Hashem. This connection is Matan Torah.
Hashem does not give up on anyone.

If you want to be close to Matan Torah you have to make achdus the basis of your life. We fell from the level of the first Matan Torah, but we have to prepare to get back there. It seem so far, but we can do it.

If a person was in the hospital for a serious illness and he also had a minor problem and his family was busy running around looking for a doctor to cure the minor illness and forgets the life threatening problem, we would call them fools. Yet this is what we are like. We focus on particulars but don't work on our achdus. What distances us from the Torah is our lack of achdus.