If you look carefully at our sedra, Moshe constantly switches between referring to Bnei Yisrael in the singular (lecha) and plural (lachem). What’s the meaning here?
I first thought that an answer could be that every time we are referred to in the plural it is in the contect of something bad, and in the singular it’s re something good. This is certainly true in the final perek of our sedra. Therefore, the message would be that when we are together (singular) like one person with one body we’ll get bracha, and if we are plural, separate, and not unified we get bad things. But though the message is correct, the theory doesn’t work out for the beginning of the sedra’s switching between sing-plural. So we need a new answer?!?!
Maybe we can answer via the Vilna Gaon. He says elsewhere that even though the brachos (and curses) are given to klal yisrael as a whole, any individual can tap into them themselves even if klal yisrael don’t all deserve them. That means that even if klal yisrael are not serving HaShem properly, if you are properly then you can get the wonderful brachos in parshas Bechukosai and Ki Savo yourself. Therefore, the message behind the switching between singular and plural is to tell us that the blessings and curses can happen to us as indivduals (singular) or to us as one nation (plural).