1. The United States is a nation that is a constitutional republic. The nations can be defined as such because for starters it has a constitution. The constitution is respected by the political parties and authorities. There is democracy in the country, so the people have the right to choose who will lead the country and represent their interests and the interest of the country.
2. China, on the other hand, despite having a constitution, can not be counted as a constitutional republic. The reason for this is that the constitution is made by only one political party, which is the leading party, and practically the only party in the country. The Communist Party has absolute control over the country, and it changes the constitution as it is in its interest, not oblige to it as it should does. Even though the people are officially allowed to vote for the representatives in the parliament, in practice the representatives are chosen by the Communist Party it self.
3. The United States have a democratic government. The bicameral system is in function, where there are two domes that independently decide about every law, which has to be adopted by both of them. This system has been established so that there isn't a situation where one political party managed to get too much power and abuse it. China has a communist government. The whole government and parliament are chosen and composed of members of the Communist Party, which are chosen by the leader of the party. The Communist Party has absolute control, changes the constitution at its will, and there isn't any authority that monitors its activities.