LONDON (Reuters) - A look at the day ahead in U.S. and global markets by Alun John, EMEA breaking news correspondent, finance and markets.

Investors fled from stocks and rushed to dollars in Monday trading in Europe and Asia, as they scrambled to process the consequences of President Donald Trump putting larger-than-expected tariffs on top U.S. trading partners.

In three executive orders, Trump imposed 25% tariffs on Mexican and most Canadian imports and 10% on goods from China, starting on Tuesday.

U.S. S&P 500 futures were down 1.7% and Nasdaq futures were off 2.2% in the European mid-morning, while the reaction in currency markets has been more dramatic.

Pretty much everything is getting sold against the dollar, with the Canadian dollar, euro, Mexican peso and China's yuan all in particular focus.

The loonie depreciated to as much as C$1.4792 per dollar, its weakest in over 20 years, while the peso is down over 2%.

But why the strong reaction? It's not as if investors didn't know that Trump, the self-proclaimed "tariff man", liked the idea of imposing tariffs.

It's partly a reversal of some - in hindsight, misconceived - optimism that a lack of focus on tariffs in Trump's remarks at his inauguration on Jan. 20 meant that he would hone in on other issues in the early months of his presidency.

The last couple of weeks have seen a small weakening in the dollar on the back of that. But that reversal has now, in turn, been reversed.

More importantly long term, the other reason for the large reaction is that the scale of the tariffs is larger than expected.

George Sarevlos, head of currency research at Deutsche Bank, said the announcements were at the 'most hawkish end" of the spectrum they could have envisaged and that if they went ahead the tariffs would cause a massive shock to global trade policy.

"We see immediate recessionary consequences for some of the economies involved and broad-based negative read-across to the world economy," he said.

The tariffs are also large compared to those imposed during the first Trump presidency in 2017-2021.

Barclays analysts have done some sums.

"In Trump's first term, the administration put tariffs on $380 billion worth of imports, mainly focused on China. The tariffs proposed this weekend by Trump would cover $1.4 trillion of imports, focused mainly on Canada and Mexico," they said.

"The tariffs in Trump's first term phased in over years. These new tariffs would be implemented all at one time."

Auto stocks in Asia and Europe have seen the most dramatic fall. Many have shifted some production to Mexico to ensure easy access to the U.S. market.

Another reason for the optimism seen among investors in January had been that a large market selloff might cause Trump to reassess his position.

There is no sign yet of that happening, however, and Trump has said the tariffs may cause "short term" pain for Americans.

As to what happens next, optimists will point to Trump saying he'll talk to the leaders of Canada and Mexico to see whether there is scope for negotiation, but hopes seem pretty limited for now.

"I don't expect anything dramatic," Trump told reporters as he returned to Washington from his Mar-a-Lago estate in Florida. "They owe us a lot of money, and I'm sure they're going to pay."

The pessimists have got plenty to point to, particularly in the European Union, which is bracing for tariffs. Accusing the EU on Sunday of not buying enough U.S. exports, Trump said of the 27-nation bloc that it was "an atrocity, what they've done."

Key developments that should provide more direction to U.S. markets later on Monday:

* Tariff news and negotiations

* US earnings: Tyson Foods ( TSN ), Cabot

* Fed's Bostic speaks on economy

(Editing by Gareth Jones)