US has not spent $350B on Ukraine. It has spent $132B, $33B of that is money. The rest is $21B in loans, repaid from frozen Russian assets, $4B in humanitarian aid, and the vast majority, $74B is military equipment.
Half that equipment is new, made in the US. The other half is old stockpile equipment, which soon would have had to be demilitarized at great cost. The replacement equipment is made in the US, so the money stays in the US.
Meanwhile, the EU and European countries have spent a combined $271B, more than twice as much as the US.