Welcome to the era of Big Data. The IRS has rapidly expanded its technology so that at a glance they can track virtually everything you do worldwide. It is no longer prudent for any American living outside the US to base any personal planning, including US tax compliance, on the assumption that the US government won't locate you. The better assumption is that more than likely the details of your financial and personal life have already come to rest somewhere in a government computer. Here are the 13 ways the IRS currently tracks you:
When the US government wants someone to become current with their US tax obligation, they don't need to squeeze any financial institution in the country where one currently resides or anywhere else for that matter. It's much easier for them to make their own assessment of what they say someone owes and to present them with a demand for payment. Then it will be up to the individual to present information disputing the tax bill, with criminal penalties attached for straying from the truth.
Whatever tools the IRS employs and whatever Washington is doing (or not doing), you can make a difference in your own financial well being by focusing on the things you can control, including the timely filing of your US taxes.