Most parish priests are diocesan priests, who serve their entire careers in one particular geographic diocese. They are rarely transferred to other dioceses, so they are unlikely to transfer across state lines. Religious order priests belong to provinces, which can cover several states or an entire nation, so they can be transferred anywhere within the province.

So, for diocesan priests, the "employer" is the bishop of that particular diocese. For religious orders, the "employer" is the provincial (leader) of that particular province.

-Joe-