What requires U.S. stocks to be traded only on U.S. exchanges? In fact a number already are traded already on a number of other exchanges, and it's trivial for them all to dual list if the financial incentive is there.
French stocks and italian stocks have FTT. Currently, there are some French stocks and Italian stocks which are listed in overseas exchanges. When foreigners trade in these stocks in the overseas exchanges, they still have to pay FTT. Therefore, using them as precedents, it makes no difference even for dual-listed stocks. Everyone has to pay FTT wherever they are traded.
If the same applies for U.S stocks when FTT is imposed, do you think this makes FTT more viable and more likely to be implemented in U.S?