Here, the Telegraph examines how European leaders might respond.
Military bases
One way affected countries might respond is by exploiting US dependency on its European military bases, which it uses for proximity to Africa and the Middle East.
While sources denied that the US would be sent packing from its German bases, an option could be for Germany to significantly increase the rent it charges for these military sites.
Trade deal
There is growing support amongst MEPs for a counter-measure to block the one-sided trade deal struck between the EU and the US last year.
Europeans agreed to 15% American tariffs, without levying any of their own, while facing a threat from Trump of a 30% tariff.
Targeted taxes and reciprocal tariffs
Reciprocal tariffs to mirror the US can be adjusted to specifically target exports that will hurt Trump’s base the most.
The French President requested that the EU deploy its anti-coercion instrument, the bloc’s most powerful retaliatory tool originally designed for use against China.
These would be a “last resort” series of tariffs and drastic trade measures against the US.
European nations could also levy export taxes on specialised machinery and products for which the US might struggle to find alternatives.
However, this is a risky move that could significantly harm European industry.
Exclusions of American products and informal boycotts of US goods by European citizens could help put pressure on the US.
Social media
The EU has already begun to use its advanced technology and data regulations against the US, fining X €120 million ($242m) for various breaches of the Digital Services Act.
Brussels could wreak havoc on US-based social media, technology and finance companies’ abilities to operate in Europe, with the ability to ban services and even cease data transfers.
Oil and gas
Leveraging tariffs on US natural gas and crude oil would be a painful solution, given that the EU purchases approximately half of US exports in this category.
However, it would be devastating for the US and could rebalance Europe’s energy supply chains in the longer term.
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