The US is the most important partner of the EU, but the relationship has been under increasing strain for some time, partly but not only because of differences over the Iraq war. The EU and the US often share a similar analysis of threats but then take different views on how to counter such threats. This has led some people to ask whether the EU and the US are actually friends or rivals. EU-US relations are also complicated because many member states consider they enjoy a special relationship with the US. Many Americans have their roots in Europe, but their forefathers often left to escape famine or persecution. Isolationism has been an important feature of American history despite the global engagement since 1945. Public perceptions are also evolving, with very high numbers of Europeans expressing distrust of the Bush administration. There are different perceptions of the EU in the US. Some view the EU as irrelevant while others consider it a potential rival. The second Bush administration has sought to improve relations with the EU, but there remain important divergences especially with regard to international law. The EU-US economic and trade relationship is the most important in the world and a stabilising factor in transatlantic relations.