The United States government is composed of three major sections. It is based on the Constitution of the United States of America that was put into effect in May, 1789. The three parts of the U.S. Government are the executive, legislative and judicial branches.

Each branch works independently of the other two, and each has its own responsibilities. This system is in place to ensure that no branch can carry more power than the other. This is called the separation of powers, which was written into the constitution.

The executive branch is the branch that most Americans are familiar with. It includes the president of the United States, the vice-president, and the cabinet. The president is the leader of the country and is the commander-in-chief of the U.S. military. The vice-president is second-in-command and will act as president if the president dies, resigns, or is removed from office. The cabinet acts as agents of the U.S. President, and carry out the duties they are entrusted with.

The legislative branch of government consists of the House of Representatives, and the Senate. Together they form the congress, which can levy and collect taxes, mint money, and establish federal courts. It can also declare war, and raise and support the army, navy, and air force to protect the country. The House of Representatives has 435 members, and the Senate consists of 100 senators, with two from each of the states. Any legislation, or new law, must be approved by both the House of Representatives and the Senate.

The judicial branch is entrusted to apply the laws created by the legislative branch of government. It has the power to create lower courts under the Supreme Court of the United States. It works closely with state courts, although they are separate.

美国联邦政府由三部分组成：立法分支、行政分支、司法分支,是对于美国联邦政府中由总统指挥的行政机构总称，其中包含历史最为悠久的主要单位——国务院、战争部(今国防部前身)及财政部皆早在1789年便已成立。

联邦各行政部门的最高首长衔称为部长(Secretary)，是美国内阁的成员;自1792年起，根据联邦法案，他们组成美国总统、副总统因故发生缺位时的继任顺序，排序在美国众议院议长和参议院临时议长之后。