By Bill Emmott, independent writer, lecturer and international affairs consultant

As America celebrates the 250th anniversary of its declaration of independence from Britain, its allies in Europe and Asia can readily see that their ties with the United States should never be taken for granted. After all it was the first president, George Washington, who warned in his farewell address in 1796 after eight years in office that America should "steer clear of permanent alliances with any portion of the foreign world". As the young country grew in population, territory and economic and political power, the ability to turn that aspiration for freedom of action into reality only grew.

Avoidance of permanent alliances is perfectly natural for any independent, sovereign nation. Alongside George Washington's statement can also be placed a famous quotation from a British prime minister half a century later, Lord Palmerston, who said that "we have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual, and those interests it is our duty to follow."

Nonetheless, despite that history, allies do not currently find it easy to understand why the 47th president, Donald Trump, is so hostile to his country's longstanding partners. The reason is not the one some Republicans and other Trump supporters want to think, namely that Europeans, in particular, want to continue to get the free ride on American defence spending that they had between 1989-91, when the Cold War ended, and 2022, when Russia attempted its invasion of Ukraine. It is because it does not appear to Europeans and Asians that America's national interests have changed in such a way as to make the post-1945 allies as redundant as the Trump team often suggests.

In particular, we cannot understand why Vladimir Putin's Russia seems to have turned under the Trump administration from being considered a major threat to America's national interests to being a potential partner. This makes Europe and America feel as if we are no longer on the same side, because we have differing views about where the main threats are coming from. That is not yet true of China, but Asian allies are right to worry that this could happen with Xi Jinping too. In the U.S. National Security Strategy that the administration published last December, neither Russia nor China was cited as a major strategic threat.

Some of this can be categorised as being personal to Trump: a consequence of his liking for deals and of his undisguised admiration for dictators and the power that they hold. However, the most important geopolitical question about how America will develop after Trump leaves office in January 2029, not just under his immediate successor but in future decades as the country approaches its 275th anniversary, concerns whether a significant part of Trump's interpretation of American national interests might persist.

Trump's orientation away from leadership of the West and towards a more independent status as one of the world's three great powers -- seen now as China, Russia and the United States, but perhaps in future with India added or replacing Russia -- can be seen as a logical conclusion to draw from the way the world has evolved in recent decades. China, now a country whose economic power on some measures exceeds that of America and whose military looks a match for the American one, demands to be given equivalent treatment globally to the United States, by which it means an equal right to ignore international law or conventions when it chooses to. So perhaps Trump is simply accepting that reality.

On the other hand, many Americans, especially in the Democratic Party but also some Republicans, believe that in any contest with China or Russia, whether military, geopolitical or economic, their country has since 1945 held a big advantage. That advantage is the network of security alliances that America has built in Asia and Europe, and the military basing rights that have come with them.

This does not necessarily mean that the now 250-year-old United States, with or without the rest of the West, should want to act as a global policeman, nor bear the sort of burdens that President John F. Kennedy pledged to in his famous 1961 inaugural speech. But it does mean that when America is seeking to achieve an international goal or to deter a threat, the alliances are there as an asset. That, at least, is what one important faction in America continues to believe.

Under President Trump, America is clearly more unreliable and unpredictable than the world has become used to in recent decades, but that is largely due to the concentration in the administration of power in the hands of one man. However, for the longer term, while that unreliability will not normally be so personal, it does appear that the country's foreign policy style and stance will vary much more between parties and therefore administrations than it did during the Cold War.

In dealing with that new sense of a very variable America, Europeans need to learn from Japan the importance of resilience in the face of bullying and the need to focus on shared interests rather than on shared values. Japan has been battered by the Trump experience, but it has been bullied by previous presidents too, most notably during the 1980s.

On the other hand, the Europeans have a big advantage compared with Japan. It is that even without America's support they are militarily capable of deterring and responding to the main security threat they face, namely from Russia. If small Ukraine can cause Russia to sacrifice more than 1.3 million soldiers to death or serious injury and can prevent the Russian Army from seizing more territory, then the combined military forces of France, Britain, Germany, Poland, Scandinavia, the Baltic States and other European nations are more than capable of blocking Russia's advances, especially now that they have raised their defence spending dramatically. For nuclear deterrence they would prefer to remain under American protection, but if that goes too they still have two nuclear powers of their own in France and Britain.

Japan, in contrast, has no realistic hope of building a military capable of blocking China's advances, nor does it have a group of regional allies strong enough to help it do so. Consequently, unlike Europe it has no feasible alternative to the U.S.-Japan alliance. If it wishes that alliance to flout Washington's words and become permanent, or at least to last for as long as China remains a serious threat, it has to continue to persuade the United States that having bases in Japan is in its national interest as they are necessary to deter China and to maintain, in the late Shinzo Abe's words, a Free and Open Indo-Pacific.

As we celebrate the 250th anniversary of one of the great political documents in history, the U.S. Declaration of Independence, persuading America that it needs its allies, both in Europe and Asia, looks likely to be the most important task that will face the West during the coming decades.