you don't have to be a genius to understand that when membership is compulsory, you are not a "union".
This has not been a Constitutional Republic since membership was militarily enforced.
This has not been a Republic since states ceased to be a factor in the federal government. Their representation was stolen in 1913. There is no 10th Amendment as long as there is a 17th Amendment. The one force capable and motivated to oppose runaway federal government was eradicated.