Well, you currently have the most ruthlessly corrupt, self-serving, and utterly incompetent president the US has ever seen. Where are these controls and why aren’t they working? Congress is supposed to be a check on presidential power, and Congress is AWOL, having literally done nothing – they may as well not exist. The Supreme Court has done very little, and Trump is working around the very few rulings that have been against him. Meanwhile important national institutions are being seriously damaged and international relations with the US are at a historic low point. So what’s being done?
ETA: I’m not sure why your post here links back to my post in the other thread. It’s not in any way responsive to anything I said there.
It’s actually the opposite. Parliamentary systems, for example, particularly those in the Westminster tradition, make it far easier to get rid of an incompetent or corrupt leader than the US presidential system. A good example is that the UK has had five different prime ministers in just the last four years.