If Biden will become the president and his goal is to strengthen us dollars then their economy may become weak since there will be a higher demand of dollars within the country that will cause a higher value in forex. Though it could be true their economy will be at a slow pace for movements in the market could not have a fast activity if the citizens would start to be more conservative in spending and slow down their consumption because of the possible shortage in the supply of printed dollars
You don't take into account that America basically lives off the rest of the world
I'm not making any value judgments about this fact, juts point it out and emphasize it. A stronger dollar would only make itself more attractive to hold, which means more imports can be bought with the same number of dollars. How can be that bad for the economy? The US has a kind of "inverted economy", and classical macroeconomics is not applicable to it without reservations