Can a phone be simfree in one country and locked in USA?

[AC Question]

I have a LG G2 phone with an AT&T ROM.
It is simfree in Israel (I use it with no problems with an Isreali sim)

Can it be locked in USA to AT&T? Or if it works in Israel it means it will work with any carrier in USA?

 

[SpookDroid]

If it works with a non-AT&T SIM anywhere, it's unlocked. If it was locked, it wouldn't take any SIM Card.