If we had an opposition leader, the message would be sent to any and all contractors - Do this work, and when Trump is gone, you will be held accountable. It will be one of your last jobs. We will prosecute in courts, but definitely- we will prosecute in the court of public opinion. You’re done.
Half the problem seems to be that American politics was never set up to have a leader of the opposition. If I remember rightly: when the Constitution was framed there weren't political parties, and the three equal arms of government were supposed to keep each other honest. Cool idea...
That unfortunately doesn’t seem to work! I regret the fact that UK doesn’t have a written constitution but wouldn’t want one modelled on the USA constitution even if we decided we need one.
The British system definitely has faults, but it's difficult to imagine a complete takeover of government by a group hostile to the very existence of the British government in the way that has happened in America.