The way Christmas Lights are wired in the US is very different to the UK.
They usually come pre-wired with a standard 3-pin plug in the end, or a transformer block with a propreitary connector (probably outputting DC), so you don't have to worry about any of this extension stuff.
They usually come pre-wired with a standard 3-pin plug in the end, or a transformer block with a propreitary connector (probably outputting DC), so you don't have to worry about any of this extension stuff.