1. We have a large homgoneous market where you can build a product and it’s expected it can succeed for hundreds of millions of Americans
2. EU is the easiest second market, and another step change of hundreds of millions of customers in a somewhat unified market
3. there’s not an easy 3rd economy that replaces EUs wealth, population, and comfort with English + technology
When we piss everyone off in the EU tech company growth gets kneecapped and limited to US / Canada. Theres not an easy market to expand to without much deeper focus on that specific market and its needs, for much fewer returns.
There's a strong desire to forge closer links with the EU now and reduce dependence on products that could be weaponized against us at any time. Geographic proximity doesn't count for much when it comes to software.
I take a more optimistic stance here. Trump can only live so long, and everybody except basically Trump and John Bolton knows that the majority of his idiotic tariffs (and nonsensical belligerence like pretending NATO control of Greenland doesn't meet all our defense needs) are wealth-destroying on net, as well as wealth-destroying for at least 10x the number of people than they help (many of them I'd say 100-1000x as many). When Trump leaves the stage, those who replace him will either be Democrats sprinting at full speed from all his policies to demonstrate how not-Trump they are, or Republicans who want to grow the economy. Either way, the stupidity in a lot of his policies is a temporary condition.
Note that I'm not saying everyone should give the US a pass or maintain as much economic and defense dependency on the US. But I think it's hyperbolic to make all your long-term plans assuming something as stupid and self-defeating as his worst anti-ally policies are a new normal, because they harm the US at least as much as they harm everyone else, and everyone but those two knows this.
It was an unusually high degree of trust, and now it's unusually low. Even if the US reverses its policies it will take a very long time to rebuild trust, and even then the historical warning marker of the Trump admin will be studied as a reason to never return to the prior level of trust.
Without total trust software products are a natural target for any country that's thinking more about how to defend its own sovereignty. Policies and subsidies for locally built software that previously would have seemed frivolous or wasteful now seem prudent and badly needed.
The UK seems a lost cause though, even under Starmer it has been far more appeasing than any (West-)EU country. And as right-wing as Starmer is, your next PM will inevitably be even moreso and more buddy-buddy with the US. Perhaps even a personal friend of MAGA.