Filipino leader Rodrigo Duterte, though, is far from a normal president. And his behavior - and that of his government - is increasingly posing a serious challenge to Washington on an ever-growing variety of levels.
Washington's relations with the Philippines have always been complex. The Philippines were one of the very few U.S. colonies overseas before they were granted independence in 1946, although the United States retained several sovereign bases. With the rise of China and growing confrontation in the South China Sea (Vietnam's East Sea), most experts believed links would become notably stronger - indeed, that assumption was one of the linchpins of U.S. thinking, particularly after the Obama administration announced its "Asia pivot" in 2012.
The election of President Duterte in May this year, however, has made that relationship increasingly difficult, if not outright impossible. So far, the geostrategic implications of that move have been limited. But the longer he stays in office - and the worse his relations become with the United States in particular and the broader international community in general - the starker they will become.
In some ways, the White House may have been relieved that in calling Obama a "son of a bitch" - or in some translations, "whore" - Duterte finally pushed things too far. The comments, recorded in a conversation with mostly Filipino journalists, prompted the White House to cancel a planned bilateral meeting due to take place in an Asian security conference in Laos. Prior to the announcement, it was already shaping up to be a diplomatic disaster.
At the heart of the problem is Duterte's "war on drugs". In his election campaign, the Filipino president bluntly pledged to reduce crime by killing drug dealers, making it clear that during his tenure law enforcement agencies would be unencumbered by anything approaching legal process.
It was, essentially, an unapologetic pledge to enforce resource a campaign of extrajudicial murder. His government has been as good as its word. Around 900 people have been killed in police operations since July 1, with a further 1,500 unsolved murders described officially as "under investigation" but which rights groups say in many cases appear to be government-sanctioned extrajudicial contract killings.
The human consequences have been deeply unpleasant. In August, the BBC profiled one of a growing number of female contract killers who said she had been paid by the government to kill several drug dealers, usually in cold blood. Unsurprisingly, public criticism of the campaign is relatively rare - not least because of rumors that political and personal scores may be being settled amid the crackdown.
Unsavory activities by America's allies are hardly new. U.S.-backed Latin American governments often ran a variety of death squads, particularly during the 1980s. Duterte, however, has made a point of boasting of the killings while demonstrating ever less tolerance for criticism. That has included threatening to leave the United Nations after condemnation from U.N. agencies and officials.
Philippine President Rodrigo Duterte arrives at the ASEAN Summit family photo while U.S. President Barack Obama chats with the Sultan of Brunei Hassanal Bolkiah in Vientiane, Laos September 7, 2016. Photo by Reuters/Jorge Silva
The outburst against Obama followed news reports that the U.S. president was aiming to be similarly critical.
The geopolitical implications make this remarkably messy. The United States cannot endorse - or even deal closely with - a leader who revels quite so clearly in tearing up the internationally accepted norms of law and order. America's entire Asian strategy, meanwhile, is dependent on building closer ties to countries like the Philippines and, ironically, stressing the importance of following internationally accepted rules on a wide range of other issues.
That's particularly true when it comes to Beijing's increasingly assertive posture in the South China Sea. Earlier this year, the Filipino government won a landmark ruling at the international U.N. maritime court in The Hague, declaring Beijing's grandiose claims of offshore territory unlawful.
Washington has been particularly critical of China's program of building military outposts on often disputed reefs, including those also claimed by the Philippines. Military collaboration with the United States has been increasing. In 2014, the two countries signed what they described as a landmark security accord giving the United States renewed access to bases. That deal had only just cleared its last legal hurdles, being declared constitutional by the highest Filipino court in July.
The Filipino government and China have some of the tensest territorial disputes in Asia, particularly over a chain of rocky outcrops known as Scarborough Shoal. What happens over them will help set the tone for the rest of the region, including other potential flashpoints with Japan, Taiwan, Vietnam and elsewhere. Officials in Beijing, one suspects, must barely be able to believe their luck.
Peter Apps is Reuters global affairs columnist. He is founder and executive director of the Project for Study of the 21st Century (PS21) think tank. Before that, he spent 12 years as a reporter for Reuters covering defense, political risk and emerging markets. Since 2016, he has been a member of the British Army Reserve and the UK Labour Party. The opinions expressed are his own.