Parliamentary systems failed in most eastern european states, in part, because

The correct answer is these states had little democratic tradition

Eastern European countries usually had a totalitarian ruler historically, whether it be a monarch or a totalitarian ruler in a communist country. That's why when the transition period began, many of them were in trouble because they did not build the democratic tradition and were not democratically educated, which caused many corrupt people to exploit the system for political power.

From mexican american war , us gained new mexico.