The difficulty of switching is straw man. In Europe, a monopoly just means a product or a company with a near-100% control of the market. It doesn't have anything to do to the presence of competitors, the difficulty of switching, if the product is a commodity or not, and so on. In Europe, Google Search has >90% market share so it's a monopoly, and thus it is subject to regulations in the way they use their product they wouldn't otherwise subject to. The same will happen to Android as they approach 90% market share; Google will be forced to do things that Apple will fully get away with, because being a monopoly makes you subject to additional regulation.

Not as easy, but it isn't extremely hard either. You can have unbuntu running on most PCs w/in an hour for free.

I also think it is worth noting that Google's only real competitor is a non-profitable Bing that microsoft literally has to bribe people to use.

Microsoft may tire of it and throw in the towel.

I'm sure you're aware that switching over to Ubuntu is not nearly so simple, so I don't need to explain hardware compatibility, backing up data, cross-platform app availability, etc. If it were really so simple, System76 and Dell's Project Sputnik would not be such big deals.

Google also competes against Yandex and Baidu, to name just two. That Yahoo uses Bing for their back-end doesn't change the fact that they're a legitimate competitor as well. It's possible Yahoo will revive their in-house search technology once their deal with Microsoft expires, too.

And speaking of counterfactuals, we can't just ignore Bing's existence because "Microsoft may tire of it". Any company would hypothetically be a monopoly if all their competitors gave up...

It's not the hardware side that gives you a massive barrier to switching OS, it's the software side.

Are you really comparing switching the search engine in a browser with changing the OS from Windows to Linux?