Indians fought in the Revolution for Indian liberties and Indian homelands, not for the British empire. The majority of these tribes fought for the British but a few fought for the Americans. Many of these tribes tried to remain neutral in the early phase of the war but when some of them came under attack by American militia, they decided to join the British.
Spain used the mission system as their main method of colonizing because they had new spain already so they could easily expand from that point. Also it allowed them to spread catholicism.
