European plates cannot be used here in exchange for your standard plates...
If you live in a state which requires a front plate, you must keep your standard plate in addition to putting on the euro one, or any other plate for that matter.
If you are not required to have a front plate, then you may put on a euro plate as it is just decoration.
I live in NJ and we require a front plate. Last year I removed it and put on a euro plate. I got a ticket for no front plate about every 2 weeks until I removed it and put the old one back on. You also get no sympathy from police officers as you not only removed your required plate, but went as far as putting on one from a different country.