Why is it easier for the Prime Minister of Great Britain to pass legislation than it is for the President of the United States?

In Great Britain, the Prime Minister comes from the majority party in the House of Commons, the country's legislative body. Thus, the Prime Minister doesn’t have to be too concerned about an opposing party blocking his actions.
In the United States, the President is in a different branch of government than the Congress. The President is part of the executive branch, while Congress is in the legislative branch. Thus, Congress has to act on ideas that the President has. If the opposing party controls one or both houses of Congress, the President may have difficulty getting his ideas passed by Congress. The President also has to be concerned that the judicial branch could declare some of his ideas that became law as unconstitutional or illegal. The concepts of separation of powers and checks and balances make it more difficult for the President of the United States to get laws passed than for the Prime Minister of Great Britain.
http://www.rogerdarlington.me.uk/USvsUK.html

https://enfranchise.wordpress.com/advantages-disadvantages-of-a-parliamentary-system/

https://www.historylearningsite.co.uk/american-politics/president-versus-prime-minister/

In Great Britain the executive and legislative branches are very closely related. When they have elections the party that receives the majority of votes will gain control of the House of Commons (lower house of the legislature). The members of that body will elect the prime minister. The prime minister will then fill the cabinet with other members of the Parliament. This is called the government. This allows for the prime minister to enact his or her policies, thus running the entire government based on their programs. The prime minister will never be from a different party than the one holding a majority in Parliament. Occasionally, a party can only reach a plurality (the most votes, but not a true majority, 50% +1 vote) on election day.  In this case a few things can happen. 1) Two or more political parties create a coalition and work together to run the government. This happened just a few years ago when the Labor Party lost to the Conservatives who partnered with the Liberal Democrats to take the reins of government. 2) The country holds another election to see if any political party can get a true majority of votes. In the United States the Framers decided to separate the executive branch from the legislative branch. This means that the president is elected independently from members of Congress and is, very often, of a different party than the majority of members in the House and Senate. This makes it challenging for the president to fully implement his or her policies.