Can someone please tell me if I'm misunderstanding how checks and blances in the government are supposed to work?

This question was asked on Facebook by another Fluther member. She is obviously more savvy than I am about politics, but her question got me thinking. I asked permission to repost it here, and she said that was fine.

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” In school they teach us that one of the great virtues of the American government is that it has checks and balances to prevent any one branch of government from being too strong. One of the checks on the president’s power is the veto override: a president can veto a bill, but Congress can override a veto with a ⅔ vote.

OK that brings me to today. The Senate previously voted unanimously on a bill – with no wall funding – that would reopen the government. Far more than enough to override a veto. So, like…. why aren’t we doing that? The media is portraying this as some hopeless standoff where the Democrats won’t support a bill that has wall funding and Trump won’t sign a bill that doesn’t. We don’t need him to sign it?? We can just override the veto??

My understanding is the reason we’re not going this route is because Mitch McConnell is refusing to bring a vote to override a veto to the Senate floor. So Trump and McConnell, two men alone, are basically holding the government hostage over the wall money.

So, like….those checks and balances are just null and void if the president is able to convince ONE OTHER DUDE from his own party, the Senate Majority Leader, to be on his side? How in the hell did anyone think that was a sufficient check?

This is genuinely not just a rant. I really want to know – am I misunderstanding something here? I am straight-up confused about how our government is apparently this broken and I’m only just now becoming aware of it. I realize a lot of that is on me for not being as active of a citizen as I should have been in the past.”