Played that 2600 cart I got last week. It's the US version so it runs faster than the PAL version and a lot smoother. Of course the colours are wrong on a PAL machine but with this game it doesn't really matter - multi-coloured Asteroids are "wrong" anyhow!!
I have my US 2600 as well with composite mod of course but that's boxed away at the minute - it needs some work to separate the audio and visual wires which need proper shielding as the picture - while very clear - gets interference when there is a sound made. The 2 wires are very thin and are wound together - so they need unsolderd and separated with some shielding (or maybe upgraded to thicker wire). I'll wait to my local electronics repair shop opens according to lockdown rules. I still need to teach myself some basic soldering.
The cart is back in its box though. I have the ROM and PAL60 version on my Harmony cart. But I like having the cart.