Has there always been a peaceful transfer of power in the U.S.?

In many countries with 'monarchies' of one sort or another, the transfer has not always been well defined as from father to son or mother to daughter, or similar, and the result has sometimes been large-scale civil war.

Even in eastern Europe, in recent times, even last month, elections of presidents have been disputed. (90% in favour of the existing president - who would believe that?!)

 And as for African countries since independence from colonial powers.....! (No, not all of them, many are good stable democracies, but there have been bloody coups in others)

Note the large-scale anti-Trump public demonstrations when he took over. The actual handover by Obama to Trump was civilised.

The peaceful transfer is characteristic of a democracy in that the voters decide the outcome, not the contestants.

There was the US Civil War, which was a dispute over the win by Lincoln.  I think we can safely conclude that that was not a peaceful transfer or power.  It was an all-out war, and it happened because the southern states refused to accept that Lincoln had won.

And of course, the very existence of the US is an example of a not-peaceful transfer of power.  Cannot claim a revolution with war as peaceful.

Otherwise, though, while there have been some instances of protests over the win when it was close, there was hardly anything even close to violent resistance.  Even the GW Bush theft in 2000 was not met with violence.  The loser has always left at the end of his term, or not tried to take power from the other guy by force.  There has always been a voluntary transfer of power.  This was even true when Buchanon ceded power to Lincoln, so it could be argued that the transfer of power was peaceful, but I think that would be ignoring the obvious fact that the southern states seceded immediately, even before Lincoln took power.

Is it different from other countries?  Well, some never even have a fair vote so there is no real change of power, and some do have revolutions and coups, so lots of countries have, at one point or another, had changes of government and power that was not peaceful.  Central and South America, for instance, were notorious for a good century or more for having few peaceful changes in power.  African nations in the post-World War II period had numerous violent changes in power.

The US usually, and mostly, has peaceful transfer of power, as is true with most western democracies. I think we lie to ourselves when we pretend that it has always been peaceful in the US.  It has not.

It was very fraught in 1800. However the Aaron v Jefferson gulf was bridged by common sense. Perhaps it can be again once you take stock and see that the differences between you are not greater than the commonalities.

'Central issues (then) included opposition to the tax imposed by Congress to pay for the mobilization of the new army and the navy in the Quasi-War against France in 1798, and the Alien and Sedition acts, by which Federalists were trying to stifle dissent, especially by Republican newspaper editors.'“But every difference of opinion is not a difference of principle. We have called by different names brethren of the same principle. We are all republicans. We are all federalists.”Thomas Jefferson First Inaugural Address, March 4, 1801

No, this dynamic was the same for example in the USSR. See a transfer of power between Khrushchev and Brezhnev.