I don't think that is true at all. Existing US credit cards have or can have PINs. It's just that they are only used for cash advances at ATMs. Chip cards all come with a magnetic strip, which will still be necessary for ATMs, gas station pump payment and those retailers that don't upgrade their card readers. So the magnetic strip will have the PIN encoded.
Warning - technical info follows. Google EMV validation methods for more info on what I'm saying below. One example here.
When you use your old-style debit card in an ATM or at the grocery store and enter the PIN, the ATM or terminal communicates with your bank to validate the PIN (and also to verify that you have sufficient funds). It's not necessary to have the PIN on the magnetic strip (and it would be a bad idea since the data on the strip isn't encrypted) since the terminal relies on an online connection with your bank. to process the transaction.
An EMV ("Chip") card might or might not have the PIN embedded within the Chip. Explanation follows.
Credit card transactions include a cardholder validation method (CVM) intended to show that the card user is an authorized user. Chip credit card transactions can have several possible CVMs, and there's a process in which the card and the terminal negotiate to determine a method common to both that is the most preferred by the card. Possible validation methods include signature, online PIN, offline PIN, and others.
Signature validation is what you're used to for many credit card transactions in the US. The terminal prints out a paper receipt which you sign and the merchant retains (one time in Germany I signed a box on the restaurant's iPad with my finger but that's unusual in my experience). Even in Europe were everyone else will probably be entering a PIN at the terminal Americans will by and large still be signing for their purchases since US-issued cards are either are set up only for signature validation or have signature validation a higher-preference method than PIN methods.
For PIN transactions there are two ways to validate a PIN, online and offline. Online PIN validation is similar to how debit cards are currently validated in US transactions. You enter your PIN and the terminal communicates with your bank to see if the PIN you entered matches the valid PIN stored at your bank. Note that in order for the transaction to complete, the terminal must have a phone line or Internet connection (hence the "online" in the method name).
Conversely the offline PIN method doesn't require any external communication. The PIN you enter is compared with the PIN that is stored, in encrypted form, on the chip in the card. If it's a match the transaction completes. Note that the terminal doesn't check to see whether you have enough credit in an offline transaction so offline transactions are limited to fairly low-value transactions like transit tickets, parking machines and gas pumps. Also note that there's no way for an old-style card or a Chip card with no embedded PIN to complete an offline PIN transaction since the validation requires a PIN stored in the card.
Most US-issued chip cards don't currently support offline PIN. Of the few US cards that do support offline PIN most have signature as most-preferred CVM. This means you're likely to be signing for your credit card transactions in Europe for a few years even after all your cards are re-issued with chips. Also note that your new Chip card still might not work at that ticket machine or unattended gas station.