What are the Similarities between the Nature of the Party Systems in the United Kingdom and United States?

-Both Nations have 2 Party Systems, with Parliament and Congress Dominated by the 2 Main Parties and Executive Branch being Controlled by 1 of the 2 Parties -Element of Multi-Party Politics in both nations. Third Parties have challenged the Executive Control. The Libertarian Party put Candidates in 2016 and 2020. The Last time a Significant Share was won by a Third Party was in 1992 (19%) and 1996 (8%) In Britain, the Lib Dems formed Coalition Government with Conservatives, and the DUP formed a Confidence and Supply Agreement in 2017