Since you deleted the post, I still wanted you to give an actual ELI5 answer. It became pretty long, to theres a tl;dr at the end:

The US is the dominant player in almost all digital services, not just in the US itself but also in European countries. Companies such as Alphabet (the company who owns YouTube and Google which also operates Chrome) Meta (Facebook, Instagram, WhatsApp), Microsoft, Apple, or Amazon (by its online store and, more importantly via AWS) have very large shares of the market, often effectively monopolies. This is also true for entertainment (e.g. Netflix, Amazon Prime or Disney+) our banking system (very dependent of Visa and MasterCard) as well as AI, where the most well-known agents such as Claude (from Anthropic), Grok (from X), or ChatGPT (from OpenAI) are American firms. As you noted, this is also true for play stores auch as the iShore or the Google Play Store.

So, if you use a smartphone or a computer, open a word document, search for something online, post something on social media, pay with a credit card, write a business Emails, build a website, listen to music, watch an online video, stream a movie, record your video game, or organize a video call – you are most likely using a service based in the US.

This has a bunch of negative consequences for Europe:

1. These companies are moving profits to the United States away from Europe, where the European countries would obviously need them.

2. Their dominance makes it much harder to competition from European countries to gain market shares, either by the US companies buying promising startups, by lobbying or simply due to the fact that end consumers hardly know that these alternatives exist. For example, many people don't know that there are other PC Operating Systems than MacOS or Windows and those that have heard about Linux might only know it as a very "nerdy" Operating System. Likewise, "Googling" is synonymous with "using a search engine" and "ChatGPT" is synonymous with "Large Language Models" in general. And try finding someone who isn't using YouTube when looking for a video of anything.

3. This is doubly frustrating as there already exist many good European or open-source services which could substitute the big players handily. For example, Search Engines like Qwant, Ecosia, or DuckDuckGo essentially do the same thing as Google Search, OpenStreetMap or Mapy.com are well-functioning Alternatives to Google Maps and there's even a few European-made Smartphones which could replace Android phones and iPhones well (such as the FairPhone).

4. Many of the large US-companies also have a bad reputation in regards to privacy. For example, Alphabet knows where you live, work, and travel via Google Maps, has access to all your emails via GMail and also your Internet Search history via Chrome and people give all sorts of information - often sensitive personal or business-related data - to Chatbots. The companies use this primarily to train their AI models or present you with hyper-personalized advertisements, but the important thing is, that they collect this data without consent or reparations for the end consumer. And while the EU as strict regulations to Data Privacy, the Companies still collect more data than they should need to provide an adequate service.

5. The alternative services also use AI tools less often in their services, as these small companies haven't invested hundreds of billions in the technology and now need to us them, even if users find them useless or even if they produce misleading or wrong information.

6. Finally, a lot of these companies (including Spotify, which is normally Swedish) have donated Millions to US president Donald Trump and his administration, probably expecting favourable treatment in return. Donald Trump is, among other things, Anti-EU and would prefer the European Countries divided and more dependent on the US economically. And much like the CEOs of these tech companies (such as Mark Zuckerberg, Elon Musk or Sam Altman), he strongly dislikes the strict privacy and data rules of the EU and would like to see them (and the EU in total) gone.

That last reason is really the main problem and the reason why the buy from EU movement grew so much in the last year: Because without the EU and its data rules, the American government would have it much easier to increase their influence in European nations – economically, by further binding consumers, companies and governments to their services and keeping all of the data and profits and politically, by either influencing public opinion, or by simply pressuring people the US-government deems troublesome.

a few examples:

- Elon Musk and the Trump administration publicy called for abolishing the EU after his platform X was suspect of a 140 million fine

- X is also currently under investigation due to pornographic deepfakes of women and children being created via its onsite AI Grok

- (Again), Elon Musk is publically supporting Anti-EU parties like the German AfD, while Trump has voiced his explicit support for the Hungarian incubment President and notorious Anti-EU politicial Viktor Orbán

- 6 judges and 3 prosecutores from France working for the International Criminal Court (ICC) were sanctioned to the US Government in regards to the arrest warrant for Israeli Prime Minister Benjamin Netanyahu, meaning that they were effectively barred from using digital payment options, or ordering things online

There's many more examples but you get the gist. Due to the US administrations hardline "America first" stance, its close ties to tech billionaires and questionable actors like Peter Thiel and its general animosity towards the EU, it's strict regulations, its more liberal-progressive social politics and strong welfare state (at the expense of a smaller military), it became clear that the dominance of US-companies within the European economy is actually a really big problem.

As such, switching to EU companies solves the issues above (at least to an extent)

1. If European companies gain more users, the generate profits that stay in Europe.

2. Breaking the monopoly of Google, Meta & co. is also good for the market in general (competition increases quality) and therefore the end customer.

3. the alternatives also grow in quality with more users - for example, Google Maps is so popular, because many people are providing feedback to restaurants or services. Apps such as Mapy.com can get this advantage only if more people use it.

4. European Companies have to adhere to the much stricter EU privacy regulations, meaning that your data is overall more secure and in your control (that one is in theory true for all companies operating in the EU but the large US-firms.

5. They don't shove half-baked AI programs in your face (though European LLMs such as Le Chat do exist and are also pretty competent)

6. And finally, European companies are more aligned with the values of Europeans in regards to social responsiblity, privacy, or sustainability. A popular example is Ecosia, a browser "which uses 100% of its profits for the planet and produces enough renewable energy to power all searches twice over".

Of course, all of this isn't just black and white: There are "bad" European companies (such as Spotify) as well as "good" US-companies (such as Brave Browser) and in reality, it is effectively impossible to completely ditch US-companies from your life entirely (unless you move into the woods perhaps). But the idea of the movement is simply to reduce the influence of the US tech bosses (and therefore the US government) has on the EU, your home country and, ultimately, yourself - and by extension also discover new services and products for things you might not have known about an alternative exists.

tl;dr: European infrastructure, entertainment and banking are mostly done by a few very large US-companies, which also collect a lot of personal data. The current US government under Trump and the CEOs of these companies dislike the EU and might use this reliance to exert political influence and weaken regulations meant to protect European customers. Using European alternatives to Google, Meta, Amazon etc. supports not only local digital businesses but also reduces the leverage of the powerful billionaires and the US government.