Earlier quoted context omitted.
Don’t know why you’re getting downvoted for pointing out the obvious: yes obviously the US and Israel will exploit the information system of their enemy if they can, and it’s absolutely rational to deny them the opportunity to do so.
Should internet and outside access be cut for people of Gaza and Lebanon too? Aren’t they targeted by Israel as well?
You might also have to consider the propaganda campaigns the US could run against an Iranian population with web access. If the population isn't more discontent now than it already was, "secretly" replacing commercial ad placements on western websites with US propaganda when the requests come from Iranian sources could make them discontent or inflame them further, which is bad for the Iranian government.