I’ve never heard anyone in the US say arse, ever. I kicked Fred in the ass for being an ass while riding his (jack)ass while watching Jackass. Arse sounds dumb. Do you pronounce the “r”?

From wikipedia:

Arse
Arse or ARSE may refer to:

Arse, British English for the buttocks (“ass” in US English)

Arse (district), a district in the South Tapanuli Regency, North Sumatra province, Sumatra, Indonesia

Arylsulfatase E, an arylsulfatase gene
Animal Research – Scientific and Experimental, a fictional animal research centre in the book The Plague Dogs