Wall Street bosses are girding for Europe to sideline American investment banks in response to the tariff war unleashed by U.S. President Donald Trump, fearing client boycotts and in a worst-case scenario, even formal restrictions. More than half a dozen senior bankers and advisers told Reuters they are bracing for European Union governments and companies to do more business with home lenders, which could quickly dent their market share. Two bank industry groups have discussed how Europe could act to restrict U.S. banks' activities in the region, two people said, and at least two major banks have also held internal talks on the matter, according to two senior executives.