This phrase is playful and can show affection for the other country, suggesting a friendly relationship. He's got a charming British accent from living across the pond.
Pro Tip 2/3
Informed Use
Use when referring to the UK and USA, not for other countries separated by seas or oceans. She often reminisces about her time spent across the pond.
Pro Tip 3/3
Informal Context
Best used in casual settings; might be too informal for official or academic writing. I bought this quirky hat from a shop across the pond.