I believe what kept it from that was the British king, sense people in America (Americans) had issues with the UK for randomly taxing them and taxing them at high prices to.
I’m not sure if that’s right, but that’s what I think
I would say it was because of all the different groups that were moving over and colonizing. between the puritans, quakers, joint stock companies, etc, there was a lot of diversity and different values in ideals, which could’ve caused tension and prevented them from uniting. i hope this helps!!