You act is if other countries need U.S.A dollars and US government bonds. Because a country like China that has massive exports to the USA all they are getting in return for their exports is worthless U.S. dollars (a.k.a. U.S. trade deficit). Its no big loss to stop receiving worthless U.S. dollars and US government bonds. They can instead resell those same goods being produced to other countries and get products and services in return rather than running a trade surplus with those countries i.e. send out goods and get goods in return instead of receiving worthless fiat in return.Retaliatory tariffs won't do anything except destroy the country that tries to tariff America since we can just raise tariffs that much more. They will need to devalue their currency even more to sell here, and the dollar grows even stronger which allows us to buy more from other countries that do not use tariffs.
It's a zero sum game theory that rewards any country who cheats - which in this case will be any country that does not tariff us.
The only way retaliatory tariffs could work against the USA is if every country on the planet agreed to retaliatory tariffs on us.
Any country that refuses to cooperate with the rest of the world can just buy from other countries, resell to America and make bank. In other words, retaliatory tariffs will quickly be discovered to be impossible. Anyone who tries will go bankrupt.
Peter Schiff has explained this point really well. The rest of the world keeps sending their goods to America and getting worthless US dollars in return. The U.S. is the world's biggest debtor nation ripping off all the other countries by exchanging their worthless fiat for real goods and services. This cannot last forever eventually the US will collapse.