I have to do my patriotic duty to remind you that SAP is the 6th/7th largest software company in the world by market cap. I know not as exiting as notepad with AI but they do exist.
That said US software giants are a disease for democratic societies. If Europe wants software sovereignty we don't need "significant large software companies" we need a hundred medium sized ones that reflect the diversity of the dozens of nations on the continent. We don't need gilded age robber barrons owning the largest communications network shaping politics. We need a democratic genuinely market respecting solution, we don't need to emulate the techno-feudalism of the US or China.
Europe needs in fact to be more ambitious than to build its own Microsoft. We need a genuinely open ecosystem which is not going to have as its goal to extract value out of its users.