This is just not true. In fact, this very article and thread talk about how various laws are added to a bill to garner support from people on various sides.

In fact you can actually see that the rate of legislation has been steadily increasing over the years.

https://www.govtrack.us/congress/bills/statistics

I won't make a statement about parliamentary systems, but believe it or not, the US system doesn't grind to a halt when the President's party is not in power, because the President doesn't just magically veto everything like a child might.