Can only US markets go higher in the face of tariffs and other trade headwinds?

In one word - NO!

One the trade front, the US needs other countries (suppliers) as much  as other countries need US as a consumer No. 1. Yet, the consumption burden falls excessively on the US. That too is not sustainable. In the natural course of things this burden should gradually pare down. This natural process was impeded by interventions in currency and trade policy by (a) East Asian economies following 1997 crises and (b) Japan first then China. 

In the first case, the impact is benign as the comparative sizes of the economies in South East Asia and US/UK etc is too big. 

The second case turned out to be problematic, though bit less, in case of Japan. Absent the computer and technology revolution, US would be in same position as today as in post-Japanese growth phase. At the time when the US jobs were diminishing in the face of Japanese competition and trade, Tech was already cooking in the oven. The massive productivity boom unleashed by tech was supported by job growth in new sectors. These sectors pulled decent quantum of current workforce and modified the training profile of upcoming workforce.

Today, there seems to be no new sector that is vigorously attracting the current workforce into itself. There are two reasons for this. First, the speed of Chinese growth is dramatically higher than Japanese growth. What Japan achieved between 1945-1980, China achieved between 1980-2000. Second, Japan started at the time of man-power constraint. China started gaining traction when manpower was becoming surplus. Therefore, job "protection" in developed world has become important.

The trade fears can be allayed / calmed if there is another sector that can create as many jobs for the profile of workforce that exists today and about 20 years from now. Absent that, growth will require  fighting for a larger share in a diminishing pie - a potent trigger for conflict.  The war can be won by biggest bully if he is alone. But when there are a few contenders it takes time to settle the pecking order. Many skirmishes (I mean trade & currency conflicts) need to happen to settle that order. For strategy suggestions we can look at how pecking order is established in prisons. The strategies will be same the tools will be sophisticated. 

Thus, US cannot do trade wars alone. US needs its own "gang". That gang was NATO, NAFTA and these days the "Quad".  The Stock markets of one gang may rise if the gangs are tighter) and they may decouple from other gang. But only US markets rallying is not possible.

---

 Buy my books "Subverting Capitalism & Democracy" and "Understanding Firms".