Nothing if Trump doesn't lead in the way that God asks of him. I understand that God will allow unfaithful people to rule or govern a nation, and we are to follow the law as long as it doesn't contradict His law (Romans 13), and all of this will work for His will.
But Trump isn't going to change the nation of the US by himself, and is no saviour to America and while interesting, I personally fail to see the relevance in the fact that Donald Trump had faithful ancestors.
I know God goes before people and sometimes prepares lineages and roles for people ahead of time, but his heritage doesn't mean he will automatically be faithful and we only have to look at his history and language behind some of his attitudes in the to see he hasn't been a follower of God for most of his life.
But even if he has since been converted, and I hope he has and only God can truly judge that, we will start to see change over time to be more Christ like.
While he holds some views that are compatible with our faith and holds prayer meetings etc, at times I don't see behaviour that is Christ-like. An example of this is threatening revenge and throwing tantrums on live TV accusing people of fake news (which does exist) etc. and not acting on professional medical advice surrounding the pandemic we're in before it's too late. Sadly, it lacks wisdom.
Only God can change America and the world if the rest of the church in the US are faithful to God.
My point is - some need to be careful not to idolise Donald Trump.