The Republican tax bill contains a provision to impose a withholding tax on foreign remittances. Initially set at 5% of the amount of each remittance, reports now state that this has been lowered to 3.5%.
It seems that US citizens may in most instances be exempt from this tax, or be able to claim an income tax credit for such withholding, but there are conditions. One condition is that the bank or money transfer company be a "qualified" remittance transfer company (RTC) and there seems to be a path by which a US citizen could be out the 3.5% tax:
The remitter is a US citizen, but uses a remittance company that is not a "qualified" RTC.
The remitter is married to someone who does not have a SSN. This applies regardless of whether tax filing status of the US citizen remitter is single, head of household, or married filing separately.
A good writeup of this proposed law is here: https://taxnews.ey.com/news/2025-1108-new-5-percent-excise-tax-proposed-for-remittance-transfers