What will you buy instead? The point is that the dollar is strong not purely because the American economy has been (and continues to be) the largest on the planet, but also because it is not currently possible to topple the US since its global activities are tied strongly to its military.
The only realistic options that exist at the moment are going back to the gold standard (not viable for most countries) or shifting to the yen (which is tied to the dollar as Japan is the largest holder of treasuries).
treasuries are overwhelmingly impacted by federal reserve policy, not sure why you think trump would have much to do with it. if you compare US vs european treasuries since 2016 it's sort of a wash - the european ones are barely outperforming US ones, but the US ones consistently had better yields. and the big impact on US treasuries was interest rate changes, something trump has no say in
The only realistic options that exist at the moment are going back to the gold standard (not viable for most countries) or shifting to the yen (which is tied to the dollar as Japan is the largest holder of treasuries).