The US has approximately 100 tech companies worth $10 billion or more. Europe, with over 2x the population of the US, has about two dozen.
Seimens is a very old - 170 years old - industrial conglomerate. That's like using GE, Berkshire Hathaway or 3M as an example.
Nokia is barely a good example. They're a $30b market cap company, Google can sneeze and lose or gain that in a day. Texas Instruments and Broadcom are worth 3x what Nokia is; Cisco is worth 7x Nokia. In a land of giants, Nokia is pretty small.
SAP is a very serious tech company, and by far the only good big tech example Europe has today. They're slow growth, have a $140b market cap, with $4b in profit (equal to about a month of Apple's profit). They're less than half the size of Oracle and will be eclipsed in size by Salesforce in the near future.
ARM was one of the more exciting European opportunities, until Softbank ate them. NXP might be able to make some good growth moves now that they're apparently not ending up in the belly of a US giant. I could see them forging a good path as an independent.
Spotify might have a bright future. They have to make a decision soon about whether they're going to be culturally an acquiring and aggressive growth company, or whether they're going to watch that extreme valuation (which they can probably never justify given the margin situation) disappear and get acquired in the next market downturn. If they play their cards right, they could be a legitimate long-term $30b-$50b market cap media/tech company (legitimate as in actually backing that up with earnings).
I think Europe's big opportunity, broadly speaking, is in artificial intelligence over the next decade plus. That's a solid inflection point where some new big companies will emerge. Europe has tons of AI talent to make something happen there (if they don't all sell out to big US or Chinese tech).