The US taxes you on wages only if you are within the borders when you do the work. So a noncitizen doing work outside the USA and getting paid by a US customer or employer is not taxable in the USA on those wages.
You would not need that intervening corporation in Ireland for income tax reasons but there are probably good business reasons for putting a layer between you and the US company.
If you are a US citizen you are taxed on your wages no matter where you are on Planet Earth. Some relief is possible (first approx $100k not taxable, for instance).