Complex sentence: Australia consisted of separate self governing colonies, each of which was still subject to the British Crown, and because the population comprised such a high proportion of British immigrants, most Australians still had strong ties to "The Mother Country".
Split into simpler sentences: Australia consisted of separate self-governing colonies, each of which was still subject to the British Crown. Due to the fact that the population was comprised of many British immigrants, most Australians still had strong ties to "The Mother Country".