The drone killings are anonymous, out of the sky, with no idea who the guilty party is besides a nebulous "USA" or "the West"; a vacuum of information besides a robotic, faceless apology in a press release (that is itself just more insult, more humiliation), and the knowledge that a foreign country can reach out and murder people living next door to you without consequence. The humiliation and rage and sense of powerlessness and living every day knowing that they'll do it again and nobody will do anything about it simply festers. These are key ingredients in growing terrorists. This is how you make terrorists. Humilation and anger and a sense of powerlessness and that the perpetrator will face no justice.
When some idiot boy shoots up an office in Paris there's a guilty party, a reckoning with a body (or an arrest), a name, an investigation and professional state employees actively going after someone, actively pursuing justice (very different to the state doing no more than shrugging and saying "yeah, that's the USA for you, they murder you and your neighbours, nothing we can do about it"). There is a qualitative difference; the key ingredients above aren't present. Even if the terrorist gets away, it's recognised that it was an individual(s) and that they are being pursued; someone is seeking justice on your behalf.
If a single drone strike is how you create terrorists, what is being created in Europe?
On the face of it, not terrorists.
