There is no general rule that parliament has to ratify, or even scrutinise, a treaty. The main exceptions are if the treaty requires domestic legislation to be passed by parliament, or if the treaty has significant constitutionap implications. Given our un-codified constitution here in the UK, I would imagine the latter constaint comes with some wriggle-room.
This [2] briefing by the House of Commons Library lays it all out.
[1] https://en.wikipedia.org/wiki/Royal_prerogative_in_the_Unite...
[2] https://commonslibrary.parliament.uk/research-briefings/cbp-...
The real lever of power in congress is the parliamentary process in the Senate.
Wyoming has more sheep than people, but they are represented on the same basis as California, Florida, etc.
The Republicans do end up with a small (up to 5%) advantage in the Senate but that's it. Nothing remotely close to the Labour party getting a near supermajority in the Commons from 34% of the vote. It's simply much much worse in practice than the situation in the United States.
Not the case. The executive makes treaties. Parliament can scrutinise them but has no general ratification or veto role. See https://commonslibrary.parliament.uk/research-briefings/cbp-... .
My point was that there is no constitutional requirement for parliament to ratify treaties.
Yes, it can delay a treaty. It could even pass legislation preventing a treaty from having legal effect. But that would require a extraordinary breakdown in parliamentary party discipline.