There is two independent possibility:
1. US introduce customs against everyone. In this case the inflation will go up, the interest-rate go up, the unemployment down, the wage growth up, and the economy grow up.
Unemployment is not going to go down when interest rates go up and inflation going up. This is a double jeopardy for business. Higher interest rates means higher costs of operating a business. Higher inflation means loss of consumer purchasing power and they buy less, which means less sales for business. Both factors can cause businesses to go under, or lay off employees, which either case people will lose jobs. Wage growth will not go up, and will likely go down, which is the other option from getting fired. When you lose business activity, the economy slows down, and eventually contracts.
Inflation needs to be precisely measured that you only allow as much inflation due to easing monetary supply to power growth. But you go beyond that and currency will weaken, consumers will lose purchasing power.
2. China dump the treasuries . In this case the the effect similar like before ( it is practically strengthen the yuan vs the dollar, so it will be a Chinese made trade barrier) , but it will introduce a very strong deflationary pressure, that will require cut of interest rate + possible QE.
Fed needs to soak up the Treasuries and mortgages yes, but they are already sitting on 4.4 trillion on it, much of that acquired in the last decade alone since 2007. You have a problem when you have an annual deficit of around a trillion, which can increase if the government revenues drop due to lessened economic activity.
The current, slow increase of trade barriers should not be a problem for the US economy to handle.
They're saying the trade war can cost the US half a percentage point in economic growth. The US economic growth is 1.6%, so that's like losing a full third.
There is not enough gold on the market. Precisely, if Russia start to buy the gold from the market then its price will explode through the roof, and the whole move will be nothing else just a transfer of wealth from Russia to the sellers of gold assets.
Practically all possible exchange of treasury to anything ( except slowly for consumer good from the US) will have the same effect.
Russia is smart.
It is important to recognise that the Chinese buying of treasuries IS the exactly opposite of the customs, it generating the trade surplus.
Buying Treasuries keeps US dollar strong, and makes US exports less competitive, while Chinese exports become more competitive. Yes. Plus the US keeps paying China many billions of interest.
But its likely China will release money to its own domestic economy for its own monetary easing to help businesses and boost local consumption. That means less money going elsewhere outside of the country.
The current Trump policy temporally decrease this surplus, because the driver of it is the treasury buying, unless there is a continuous adjustment of level /type of customs/barriers.
That's not Trump policy. That's the current Fed policy, which imposed quantitive tightening for the first time in years since 2007. Fed policy and Trump policy is not the same, as the Fed operates independently from Trump administration, and will do things for the sake of what they believe needs to be done for the country, and not to further Trump's ego.