There are many plausible scenarios in which the dollar ceases to be the de-facto currency. They all have a few things in common. For people to stop using dollars for international trade, there would need to be two circumstances:
- A reduction in trust in the USD (not just in US politicians)
- A good (better than the USD) alternative currency
While political emotions run strong, both in the US and abroad, these emotions do not normally have a large effect on the economy. There has been no significant change in American business practices, law, monetary policy, or productivity as a result of the change in leadership. This has been very clear. You can easily argue that American reputation abroad has been harmed, but that doesn't translate to negative economic repercussions. Remember, the Soviet Union was using the dollar for international trade during the cold war. A reduction in trust in the USD would come about if there was significant inflation of the dollar or if the US stopped producing things that people want to buy. Neither of those appear to be on the horizon. As the result, there has been no change in the attitude toward the dollar.
At the same time, the best candidate by far for an alternative currency, the Euro, has had significant problems recently. It doesn't matter if the world thinks very highly of European politicians and dislikes American politicians; they aren't going to switch from dollars to Euros unless they perceive Euros to be a safer and more liquid currency.
Similarly, foreign investors will not withdraw from American investments wholesale unless they perceive a real risk to the investment potential. These types of decisions (on a large scale) are made in a cold, calculating way. Until something happens that might actually affect the potential of US-based investments, there won't be a large change in demand for them.
Interestingly, when there are shakeups in the US economy (like when treasury securities were downgraded) the result is often the opposite of what you might expect. There's a general concern about the worldwide economy and then a flight to quality, causing an increase in demand for relatively safe US securities, including the ones that were the apparent cause of the panic.