ORLANDO, Florida, April 16 (Reuters) - Treasuries are not the only 'safe haven' U.S. asset getting the cold shoulder as investors around the world rethink their enthusiasm for all things America. The shadow over 'Big Tech' is darkening and lengthening too.

In recent weeks, the global trade war, the Trump administration's 'America First' agenda and its apparent disdain for the post-war world order have dramatically slowed inflows into U.S. markets, and in some cases, reversed them. What used to be considered some of the safest shelters from crisis are now looking a little flimsy.

It might seem a stretch to put shares of U.S. technology and chip companies, such as Nvidia, Apple, and Amazon, on par with IOUs of the federal government, but these cash-generating emblems of 'U.S. exceptionalism' certainly seemed like sure things up until recently.

As these firms' global dominance spread over the past decade and their market footprint reached an unprecedented size, they effectively become ATMs for shareholders, generating record profits running into the hundreds of billions of dollars.

In the fourth quarter of last year, the 'Magnificent Seven' - Nvidia, Apple, Amazon, Meta, Alphabet, Microsoft and Tesla - accounted for a record 35% of the S&P 500's market cap, with a combined valuation of around $17.5 trillion. Credit ratings on some, like Apple, are the same as the U.S. sovereign rating, and yields have even traded below Treasury yields on occasion.

Investors of all stripes wanted in, from domestic to foreign, retail to official.

And who could blame them? The 'Mag 7' appeared to offer the best of both investment worlds: a high income-generating asset and a safe-haven. So much so that the Swiss National Bank has a quarter of its $150 billion equity holdings in Apple, Nvidia, Microsoft and Amazon, and half of the $1.8 trillion Norwegian wealth fund's record $222 billion profit last year came from U.S. tech.

REALITY CHECK

But that sweet spot is gone. The 'American exceptionalism' narrative has been undermined, as the U.S. economy looks set to slow and America's AI invincibility has been shattered by China's DeepSeek. And now tech companies find themselves on the front line of the global trade war.

Washington is issuing new export licensing requirements for Nvidia's H20 AI chips to China. Nvidia said it faces $5.5 billion in charges, and its shares once tumbled 9% on Wednesday, wiping nearly $250 billion off its market value and dragging the broader semiconductor index down 4%.

To be sure, U.S. tech has been getting slammed since mid-February, as investors have begun to re-evaluate the sunny outlook they had for the industry under a Trump presidency. The semiconductor index is now deep in a bear market. It has lost 30% in just two months and valuations have come down much more than the wider S&P 500.

U.S. Big Tech is suddenly vulnerable on multiple fronts. Tariffs and trade restrictions from Washington will bite, as will retaliatory moves from China. And if Europe really wants to hit America where it hurts, tech is an obvious target.

WHAT GOES UP...

But it's also worth remembering how much Big Tech outperformed on the way up. They were - and remain - incredibly profitable. According to LSEG figures, the Mag 7's net profit margin hit a record 25.8% in the fourth quarter, nearly double the S&P 500's 13.4%.

Nvidia's value rose 10-fold in two years to more than $3.5 trillion, Mag 7 stocks more than doubled between October 2023 and last December, and these companies accounted for almost all of the market's profit growth in 2023.

While that halved last year and is expected to decline further this year to around a third, there is still a lot of air left to come out of the balloon. According to Bank of America's latest global fund manager survey, 'long Mag 7' was the most crowded trade for 23 consecutive months until April.

And what was it replaced with? Long gold, one 'safe haven' that isn't giving up its title.