As far as I know, there was literally Irish slavery in the Caribbean Islands by the Cromwellian times, I don't know much further than that though.
No that's
penal servitude/transportation where instead of locking up someone you ship them to the colonies and make them work for the duration of the sentence (which might be life). However penal convicts had some rights and their children were born free, unlike slaves (who were exclusively African).
Slaves= No rights, inheritable, exclusively Africans.
Penal Convicts= Very few rights, not-inheritable, from the British Isles, including Scottish and English as well as Irish.
I don't see much economic opportunities outside the Southern Plantations. Most of the rest of the colonies would be just as unpopulated and unattractive as New France if it we don't have starving Germans and Huguenots. I'd guess that in the northern colonies we would have a great majority of German-speakers in the countryside with the English-speakers concentrated only in the cities.
I'm sorry but that's just wrong. The standard of living in colonial New England was considerably higher than in Old England and people knew it. The high cost of transportation meant there were basically thee ways of getting across the Atlantic, group together via a Church or Sect and hire/buy an entire boat (Puritans/Amish), be rich enough to fund it yourself (
Virginia Cavaliers), or sell yourself into into
indenture where someone paid for your ticket and you worked for them for a number of years (normally 3-7). The 3rd option was by far and away the most popular method of getting to the 14 Colonies and provided 80% of the white immigrants by some estimates. Most indentured were British especially in the early years due to the preferences of the employers/sponsors. Continental Europeans only started to come over in the 18th century after rising prosperity in Britain reduced the attractiveness of selling yourself into temporary servitude. So unless either the Colonies are much poorer than OTL or Britain much richer you are going to see a similar thing happen. Either way you are not going to get a German speaking America.