I can't even imagine a situatuion where this is not preferable. For example, if the US immigration check happens in Ireland, they can't detain you or mess with you in ways in which Ireland doesn't approve of, which they could if you were on US soil.

If anything, it seems to me that the USA agreeing to perform immigration checks in Ireland and accept them when you reach the USA is a(n extremely mild) limitation to US sovereignty, not to Irish sovereignty.