That has nothing to do with the issue at hand. All tax codes are complicated, and you can always spend days minmaxing your taxes (or hire someone to do that for you).
But the US is unique in the developed world as making filing taxes hell even if you don’t try to minmax them, and that is primarily due to tax filing companies lobbying against the IRS doing what everybody else does (and secondarily due to the GOP very much wanting filing taxes to be as painful and error prone as possible, and for it to be as expensive as possible for the IRS).
But the US tax code is an order of magnitude larger than the Swedish one. Which probably means that it is several orders of magnitude more complex (however that might be defined).
But the US is unique in the developed world as making filing taxes hell even if you don’t try to minmax them, and that is primarily due to tax filing companies lobbying against the IRS doing what everybody else does (and secondarily due to the GOP very much wanting filing taxes to be as painful and error prone as possible, and for it to be as expensive as possible for the IRS).