Can you become a commercial airline pilot in Europe while being monocular
Pilot certificates don't give you permission to fly in a location, they give you permission to fly an airplane registered by that authority anywhere in the world. In other words, if you have an FAA pilot certificate you can fly a US registered airplane no matter where it is. If you have an FAA ATPL and appropriate class of medical you can work for any airline that flies US registered airplanes. The same is true for any licensing authority. 

The reverse is not true, you could not get a FAA certificate and fly a UK registered airplane, for example, even if it was in the US. There are some cases where you can get a local certificate on the basis of another equivalent certificate, but I believe you always need to be able to pass the local medical.