[netsharc]

Unless you're a citizen of a EU country you need a residence permit (people call this "visa", but technically they are 2 different things) to work in a EU country. As a US citizen, you can visit for 90 days without a visa, but after that you'd need something.

AFAIK if you have a grandparent who is an Irish citizen and was born there, you can get an Irish citizenship. That is automatically an EU citizenship, and if you have that you can live and work anywhere in the EU without needing any sort of permit.

But even if you have this Irish grandparent, you can't just move into a EU country and live there BEFORE getting an official document saying you are now an Irish citizen.