While it may not be a literal blood pact with the government, there have been numerous accounts of Chinese (ex)-citizens being coerced into taking actions under the threat of harm to their family and relatives that remain on the main-land.

Blood pact is a poor choice of wording, but not too far off from the reality. Perhaps blood-line persuasion is better?

The difference is in the structuring of the 'law' and government, which are very different between those countries. I put 'law' in quotations because from my perspective, US citizen, CCP's form of government doesn't work within anything similar to a framework of democracy, rights, and founding principles like the US.