On February 14, 2013, the US and Switzerland signed an intergovernmental agreement (IGA) implementing FATCA. FATCA is a US law that was enacted to improve tax compliance and combat international tax evasion. The agreement permits Swiss banks to share information with the IRS about US account holders. The agreement can be found here, and the Swiss announcement can be found here.
On February 14, 2013 the Treasury Department announced that the US and Poland signed a new tax treaty that, once it is ratified, replaces the current tax treaty signed in 1974. The Treasury release states that the new treaty includes a comprehensive limitation of benefits provision, and also includes provisions for exchange of information between competent authorities of each country. The new US, Poland tax treaty can be found, here, and the Treasury release can be found, here.
If you are unsure about how these agreements my affect you, please contact a tax professional.