The Roman Republic lasted almost five centuries (509 to 27 BC) before becoming the Roman Empire. The American Republic (aka USA) has taken a little over two centuries before becoming the American Empire. In what ways has this already happened?
(1) The “judicial usurpation of politics” — i.e., the overruling of the legislative process by the personal opinions of Supreme Court justices. In the earlier years of the republic the judicial branch focused on enforcing the provisions of the Constitution without regard to their own opinions of those laws. In the later years justices started substituting their personal opinions for the text of the Constitution, or what is equivalent, resorting to tortuous interpretations of the text which embodied their personal opinions. Then justices began to ignore the Constitution and made judgments from their own opinions, at first when the populace was divided. Finally, they took on the power to review the intent of all legislation and reject anything that was contrary to their personal opinions. No one was able to stop them.
(2) The “rise of the imperial presidency” — i.e., ignoring the legislative process by the personal opinions of the President. In the earlier years of the republic the executive branch focused on enforcing the provisions of the Constitution and the laws of Congress without regard to their own opinions of those laws. In the later years Presidents started substituting their own personal opinions and taking actions without regard for their legality. This was first seen in the use of the armed services for waging war apart from any declaration of war by Congress. It was expanded to the issuance of regulations without authorizing legislation and the making of treaties without confirmation by the Senate. It would then be possible for Presidents to postpone or cancel elections and declare themselves President beyond their term or for life.
(3) The permanently obstructed legislature — The degree to which Congress has been divided is greater than the degree of agreement required to pass legislation. The Framers purposely made the Congress both the most powerful branch of government but also its most divided in order that the power of Congress would be limited. However, as the populace became more divided Congress reflected that division and became increasingly unable to agree on even basic legislation such as an annual budget. With the power of Congress blocked, the other branches of government were able to fill the gap by going beyond the written Constitution and legislation.
(4) With Congress increasingly impotent, the voice of the people was only heard in the election of the President, which became increasingly the election of a strongman or caudillo, as they are called in Latin America. The people came to expect that they were electing a strongman rather than a President (literally, one who presides). The republic faded into the background as politicians were denounced, that is, people rejected those who followed a democratic process with its time-consuming compromises and back-room deals. As the phoniness of politicians was replaced by direct leadership, politics became the process of electing an autocrat to take charge. The empire was born.