Don't do it. The level of complexity you are looking at is mind boggling. You will find it difficult, if not impossible, to even open a bank account. Use an Irish limited company unless you want to paying lots of money in professional fees and, even with that, a large level of uncertainty. The Revenue appealed a Tax Appeal Commission decision to the High Court and whether a US LLC is opaque or transparent for tax purposes in Ireland. If these terms mean nothing to you then don't go there. The HC decision is reserved by the way.