He also reportedly called Germans "very bad" for selling millions of cars to the US. A video of him shoving Montenegro's prime minister has gone viral on the Internet.
What Trump did must have broken many Europeans' heart. NATO has long been a US-led alliance. Now Trump seems to want to turn NATO into a corporation. He cares most about whether the US gain matches its payout.
If Trump reviews the trans-Atlantic alliance from the perspective of a businessman, what he sees would be different from his predecessors.
The political and military situations in Europe today are different from the Cold War period. The threat from Moscow is less real and Russia is no longer a global rival of the US. NATO's value for the US is declining and the organization has become more of a tool to maintain the European order.
In the age of globalization, relations between major powers are less intense and have, to some extent, changed the nature of international relations. However, the three Baltic countries and the former members of the Warsaw Treaty Organization are still feeling uneasy, and the Western European nations are feeling a bit lost. It's the best time for Washington to raise the price.
The US has built giant security assets overseas in the post WWII era. Now that the US economic advantage has become less prominent, what Trump wants to do is to "sell" some of the geopolitical assets in exchange for cash.
By demanding more input from European members, Trump is actually diluting US share. But how far would he go? We believe that maintaining US' absolute control over NATO would be Trump's baseline.
Therefore, it is unlikely for Trump to ruin the US ties with the allies, nor would the establishment forces in the US allow him to do so.
Trump has shown limited interest in traditional geopolitics. Trump probably understands that mixing politics with business rules requires skills. He significantly increased the US defense budget and bombarded Syrian government forces, holding a calculator in one hand and a missile in another.
Trump is the first Western leader who disruptively uses international diplomacy. Other Western leaders can hardly keep up with him, let alone oppose him. However, whether Trump would be able to win the game is another question. Many forces do not recognize Trump's dealing of cards and together they possess the capital and possibility to tackle him.