This would probably affect people the most:
“Instead of the 30 percent withholding tax presently imposed on U.S. source income
received by nonresident aliens and foreign corporations, interest and royalties would be
subject to a 10 percent withholding tax rate. Generally, dividends would be subject to a
15 percent withholding tax rate. Dividends would be subject to a lower 10 percent rate if
paid to a recipient that owns at least ten percent of the shares of stock in the
corporation, subject to limitations.”
TLDR: Withholding rates on dividends from US stocks reduced to 15% from 30%
Also for retirees with 401Ks/IRAs living in Taiwan who are not US persons, possibly their retirement withdrawals aren’t subject to the usual non-resident withholding tax rates.