No, not a USA-ism, we'd likely pronounce it the same way, although I can't think of any highway numbers that are that high. An example would be I-440 in North Carolina, it gets pronounced "eye four forty", or I-195 would be "eye one ninty-five".
The interstate system is a bit of an oddity numbering wise as well.
"Four forty" is a better way to say it than "Four hundred forty" because the hundreds place is used to denote branches off the main interstate. I440 should attach to I40 in at least two places based on its number. And checking it on a map, it does look like I440 is a beltway through Raleigh.
Also, I can see an I540, which means a spur off of I40 that. And you can see that I540 connects to I40 in one spot and deposits you near I87.
