Let's say you're running for president, and you win by a mudslide. What would you change about your country and why? Would you make new laws? Paint the White House blue? Tell all!
Win by a 'mudslide'? The idiom is 'win by a landslide'.
The thing that surprises people is that the United States presidency doesn't doesn't confer upon you powers as all encompassing as suggested by this question. There's no ability to unilaterally change much but at the edges, and as Schoolhouse Rock taught me, laws are born in Congress (although the president can 'lobby' for bills he'd like to see introduced).
Now, if I had won by a landslide, I can only presume that the agenda I ran on was popular and would work to implement it as best I could. That said, I doubt my preferred agenda would give me an electoral landslide. (Not even Obama won by a landslide -- counting the popular vote he had a good but not overwhelming 7 point victory. That was augmented by the collapse of the economy on George W. Bush's watch.) I would absolutely raise taxes and close various loopholes that let companies like General Electric pay zero taxes. I would put this money into a program to repair our infrastructure and invest in mass transportation, clean energy, and education. This would be Stimulus 2.0 This would be hard to sell to a population that thinks that the government funds mostly waste and foreign aid. It's not true, but it's a myth that makes people think you can balance the budget and cut taxes and preserve "the stuff I like".
Obama took a crack at reforming healthcare which is a good start, but I would continue pushing toward a universal healthcare system like Medicare for all -- so we aren't the last civilized country in the world where children can die of a rotten tooth because mom couldn't afford insurance. Despite what the Republican Party has been saying, reforming healthcare will save money, and do so without kicking families off heating assistance.
I'd lobby for citizens in the District of Columbia have voting representation in Congress. This is one place where I will not pretend the Constitution is a divinely inspired and perfect document. It is wrong here, and if it needs amending to grant citizens in DC the same representation I get by living just five miles away, I will lobby for that.
I can already see my landslide slipping to a squeaker. If I get a victory at all.
I will support the right of members of the same sex to get married and serve in the military. Yep, there goes the vote of the religious right.