I just compared my US shared hosting package with your enterprise package H365 (because it's the closest in similarity specs wise). I was expecting a bigger difference in specs/price but they actually compare better than I thought they would. Note I haven't hosted with H365 so I can't compare quality of service.
The comparison below I'm sure is typical (probably worse) specs and price wise between most US vs Irish hosting packages, just different scales.
Comparison: My US hosting is $7.95pm and Irish package is €9.95pm (small saving there). US host provides 20,000mb storage and 400gb bandwidth vs 10,000mb/100gb, they also provide unlimited emails vs 250/1gb. All other specs are pretty much the same however your package does allow 25 extra domains to be hosted (big plus there imo) and it is Irish based so it does seem to even out pretty well from an Irish perspective.
Overall I'm pretty happy with my current US host though, differences with page load times are slight, uptime is good, customer support is good and once your domain is .ie, hosting in Ireland doesn't seem to add all that much more in SEO weight, from what I see at least. Having said all that for critically important websites I'd always choose Irish hosting above US hosting, for the slight extra speed, slight SEO advantages, possibly because of the same timezone, possibly because the client base is smaller (not over populated) and of course it's always good to support local businesses.