I am from Dublin and now I'm in the US. I visited accountants over there to gather as much info as I could a few years ago. Smaller firms are very willing to set up a company for you to avail of the 12.5% corporate tax rate but they seem unaware/don't care about the legal jeopardy this puts US residents in. There is the foreign controlled company issue and also issues with how you pay yourself from the company. "Greentradertax" (US tax accountants) have addressed this and more in detail on their blog.
US "persons" (citizens and green card holders) are taxed on their worldwide income no matter where they live. Setting up an offshore company as a US person does not get around that. There is a tsunami of money flowing through Dublin to avail of the low corporate tax but its not US traders. US private equity firms and large US commercial real estate funds do have tax efficient structures running through Ireland but that's a different business. Google "ICAV structure" what a solution if you were allowed to avail of it (but you can't).