[inertial]

Relevant for non-residents / foreign owned LLC :

https://onlinetaxman.com/us-llc-tax-haven-for-foreigners/

If you don’t have a dependent agent that substantially furthers your business in the US and don’t have an office in the US, you are not subject to US tax. Even if the LLC generates income in the US, the income is not taxed in the US.

Furthermore, if you reside in a country with an applicable tax treaty with the US, then you would not be subject to US tax. Since you reside in your tax home, you can claim you operate a “permanent establishment” (e.g., an office or other fixed place of business) in your home country.

[sireat]

When does it makes sense for a European to start a Delaware LLC?

Let's say you have a lifestyle side-business and many clients in US.

Where is the legal tax avoidance here?

You still have to report the pass-through income to your home country.

You can't just keep the money in the LLC and delay the tax?

Maybe you want to buy 10 servers in US to be used and shipped home to Europe to be used for the same business.

Would you be able to deduct those kind of expenses?

PS I had a vanity Delaware C Corp in in the 90s which I did absolutely nothing with besides getting all the cool corporate knick knacks.

[inertial]

There are many countries where Stripe etc. aren't available. Starting an LLC in USA is an easy route to get that going albeit at additional compliance cost (e.g. filing informational returns). The article above clarifies that a foreign owned LLC with no income connected with US doesn't have to pay taxes in US. They just have to pay tax in their home country. It makes it more appealing & easier to start an LLC.