My point is that the POTUS of the USA has means to churn up hundreds of billions of USD and ask nobody for permission for it.
That's what I suspected your point was. You were not comparing apples to apples, were you? The Congress in this case has clearly and flatly refused to fund a Wall for President Trump under present offers. Trump is saying "**** that, I'll just escalate the rhetoric, declare a national emergency and build it anyway."
That is overriding the checks and balances that have stopped our leaders from having free reign.
No, I dont think it is affecting the checks and balances because the Executive branch has to manage its own costs. Our Federal budget is too big for Congress to micromanage it very well, in fact they only 'drill down' a few levels in the budget with most agencies and then let the Agency decide what and where to spend the budget given for that department. This is the 'pots of money' Trump is having the Executive branch dig around for, unspecified funds.
Now Congress can prohibit the expenditure of funds for certain things, like no toilet paper for the DoJ, but that only with holds the money that comes from the annual budget. The Executive branch has other funds available that it can use that is outside that funding. It wasnt really an issue until Pelosi and Schumer decided to deny Trump his pet project which is securing our border with Mexico which is wide open and totally unsecure for hundreds of miles.
Pelosi and Schumer used to want the wall and have both given speeches demanding one, but with Soros funding so much of the Democratic Party today, and Soros opposes the wall, so now the Dems are singing his tune since he hired the band.
But I am pretty sure the wall will be built in the guise of a double line, 30' steel slat system with a service road in between and periodic towers and concertina wire along the top. Electronic/drone monitoring would enhance that and be more effective than a concrete wall that was supposed to have been built under Bush the Younger and Obama.