Parshas V'eschanan- Shema Yisroel

Shema Yisroel Hashem Elokainu Hashem echod. This sentence is usually one of the first and the last uttered by all Jews- the posuk of kabolas ol malchas shamaim. The words 'Hashem Elokainu Hashem echod' are generally accepted as the main part of the declaration of Hashem's kingship and the first two words are just a prefix. Is that true? Or are the words Shema yisroel a vital part of kabolas ol malchus?

After tachnun we address Hashem as 'Shomer'- we daven that he watches over us- with three different merits. The first is for we are Yisroel and we say "Shema Yisroel". The second is for we are one nation as we say "Hashem echod" and the third protect the holy nation who say "kadosh kadosh kadosh". Let us concentrate on the first two. When we ask Hashem to protect us in the merit of saying "Shema Yisroel" what does that mean? Are we referring to the verse as a whole and we just say only the words "Shema Yisroel" for they fit poetically, but in essence we mean the words that follow which are "Hashem Elokainu Hashem Echad"? If so what it is the same as the second merit. Or is there a deeper meaning to the specific words "Shema Yisroel"?
I once heard in the name of R' Y. David Shlita (then found it in a wonderful book 'tachnun') a beautiful answer. To accept Hashem's kingship is the first thing every Jew must do, but there is one thing which we must do before we can even start. In order to talk of Hashem we must first and foremost be part of Knesses Yisroel, we must belong to the nation which is one with Hashem. After we accept upon us the achdus of the entire nation of Yisroel may we address Hashem and accept his oneness. We start the most awesome verse with a prefix "Shema Yisroel" - I am a part of the great nation of Yisroel and I am ready to proclaim to the world "Hashem Echad". Our first tefillah is to protect us because we are the nation of Yisroel- that alone is a reason for meriting divine protection.