原标题：台神秘无人潜艇频繁现身 专家：技术瓶颈难解决
In recent years, the U.S. domestic politics has been mired in infighting, with key issues affecting government operation, people's lives and national development have become partisan bargaining chips. A real-life version of "House of cards" is playing out. (Wei Chenxi, Yang Xin)