The real top risk is 45's presidency and the Mueller report. The outcome of it and how trump attempts to manage it will have repercussions around the globe. And when you consider his unpredictable, ego-maniacal nature, just about anything's possible.
His trade policies are behind the volatility in the stock market and if impeachment proceedings begin, it may get MUCH worse...which will affect other global markets negatively.
Desperate times call for desperate measures and as a president fighting for his and his family's future and freedom, who's to say what diversions he uses to save himself...but sink the country. The shutdown shows he has zero regard for anyone not named trump.
I could go on and on about potential risks 45 could unleash due to his policies or lack thereof...immigration crisis, potential wars, climate change, but Mueller's report and response by the government will be a pivotal time in not just US, but world history.
By electing the least qualified head of the most criminally minded administrations in US history, trump's base and the GOP should be held responsible.