Are employers to hiring Euros/non-USAyans?

Yes, this shouldn't be a problem, especially if you're Irish.

Do they ever reimburse relocation?

Sometimes, though it depends on the job. It's more likely if your particular skills are in demand

Did people locally feel accepting / genuinely friendly?

Overall, yes, although there's some regional variation

More than anything I'd say it really depends on where. There are cool parts of the US, and then vast landscapes of absolute dog shit