The lack of ability to raise taxes to operate the national government, and the requirement for a unaimous vote of the state's to pass legislation. The federal government had no way to force the states to obtain the funds it needed to operate. State only sent funds it needed to operate.
The Second Congress managed the Colonial war effort and moved incrementally towards independence.
Hope this help
Because the third estate wanted to to reduce the power of the clergy, but the church was one of the most important things to society. Hence the church having it's own country (the papal states)
The Truman doctrine and NATO were United States responses to the communist threat after WWII.