The Parliament being sovereign, it can pass an act about anything. It could certainly pass an act forbidding the government from ceding territory to a foreign power. However, since the current government holds a majority in parliament, in practice it won't happen.

It has a veto role in the text you cite (I mean, its described as an infinitely renewable 21-day delay, but that's functionally a veto, especially since the government is subordinate to and can be dismissed by Parliament during the delay, and replaced by a more cooperative government; treating the UK as if it had coequal executive, legislative, and judicial branches like the US is an error; in the UK, Parliament is supreme and the executive and judicial powers are subordinate to and contingent on its support. The government’s power usually isn’t opposed by Parliament not because the government is equal or more powerful, or has true independent powers that the Parliament can't check, but the reverse—“the government” is established from the leadership of the Parliamentary majority, and they are absolutely dependent on continued support from Parliament, so they don't, outside of the most exceptional cases, do anything that doesn't have at least tacit support of the majority of Parliament in the first place, so there is nothing to have conflict overm)

The US system is far more dysfunctional — we have the Senate, which ensures that there isn’t an opportunity to conduct a vote along any line!

The real lever of power in congress is the parliamentary process in the Senate.

Yeah, the real difference is that in the US, there is a separate election for president. In the UK, as in many other countries, the party that wins parliament gets to form the government (and determine the prime minister or whatever the title of the de facto head of the executive is). In some countries this is complicated by multiparty systems where coalitions are required, but the general idea of aligning the legislative and executive branches in this way is fairly common.

Bare majority, and with our whipping system and current parliament (massive one party domination) it will go through with ease. It has to go through the House of Lords too, and the current government don’t have a real majority there but they’re extremely reticent to oppose the democratically elected house so it’ll likely sail through there too.