Answer:
Similarities
American law was based on Roman in many aspects, and got much of its earliest ideas from the Roman Republic, including the decision to create a republican government instead of a democratic one like Athens.
The Rule of Law over the arbitrary wills of tyrants, officials, and kings.
Liberty for all citizens
Due process for all citizens, none can simply be punished without a trial of some sort
Both had written laws that created their forms of government, The US Constitution and the Roman Twelve Tables.
A Republican form of government with an Executive branch(The President of the USA and the two Consuls of the Republic)
A senate that created the laws and decided on general policy for the nation.
Both nations required military service of its citizens, especially earlier on in their history.
Citizens are given rights based on liberty, and personal freedoms over that of non-citizens.
Laws that are based on precedents and codified laws.
Laws started out focusing on the rights of the few, and expanded them over time.
Policies of Assimilation in conquered/annexed regions
Expectations of loyalty of its citizens.
Intense nationalism and feelings of having to support the nation in its endeavors.
One of the easier ways for a citizen to achieve political fame and political positions has been military glory and success for both Rome and America.
Picture
Imperial America personified in a manner very similar to a Roman Goddess
Differences
While Roman and American citizenship were very similar in direction and ideas, they had quite a few differences when it came to the rights and responsibilities they thought were important.
Women had no rights in Ancient Rome, and neither did non-citizens.
Slavery was legal in Rome, Abolished in the United States following a Civil War
America gave rights and citizenship to minority groups, women, and indigenous peoples
America suspended compulsory military service in the 1970s following popular shift against the idea.
America had no official language, religion, or many other things that most nations have had.
America prioritized personal freedom over service and submission to the state, like Rome.
America stopped oppressing native and other groups within their territory in time, and though social ills still exist in the nation, it has made significant progress towards true and total equality regardless of any aspect of a person's self.
The average citizen of the USA has the opportunity to voice their concerns to the government, and most of the power is in elected officials
The military is second to the nation itself, as the President is a civilian and the Commander-in-Chief of America's armed forces.
Military leaders are not given positions of power by their station alone, and no one in the military of the USA can serve in political office during their time in the military.
Religion is separated from matters of state in the USA (at least in theory) while in Rome being a priest was a high political office and important to the government.
Rome's economy and culture was geared towards warfare and conquest, while America's has been geared towards freedom and liberty, and more recently towards advancing the cause of social equality.
Universal suffrage in America, unlike Rome's very limited suffrage.
Women are not the property of men in America.
Non-citizens get some protections, just not nearly as many as American citizens.
Explanation: